Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
According to sociologists, there are several different ways in which a person may become recognized as the leader of a social group in the United States. In the tamily, traditional cultural patterns confer leadership on one or both of the parents. In other cases, such as friendship groups, one or more persons may gradually emerge as leaders, although there is no formal process of selection. In larger groups, leaders are usually chosen formally through election or recruitment.
Although leaders are often thought to be people with unusual personal ubility, decades ot research have failed to produce consistent evidence that there is any category ot “natural leaders”. It seems that there is no set of personal qualities that all leaders have in common; rather, virtually any person may be recognized as a leader if the person has qualities that meet the needs ot that particular group.
Furthermore, although it is commonly supposed that social groups have a single leader, research suggests that there are typically two different leadership roles that are held by different individuals. Instrumental leadership is leadership that emphasizes the completion of tasks by a social group.
Group members look to instrumental leaders to “get things” done.” Expressive leadership, on the other hand, is leadership that emphasizes the collective well-being of a social group’s member. Expressive leaders are less concerned with the overall goals of the group than with providing emotional support to group members and attempting to minimize tension and conflict among them. Group members expect expressive leaders to maintain stable relationships within the group and provide support to individual members.
Instrumental leaders are likely to have a rather secondary relationship to other group members. They give orders and may discipline group members who inhibit attainment of the group’s goals. Expressive leaders cultivate a more personal or primary relationship to others in the group. They offer sympathy when someone experiences difficulties or is subjected to discipline, are quick to lighten a serious moment with humor, and try to resolve issues that threaten to divide the group. As the differences in these two roles suggest, expressive leaders generally receive more personal affection from group members; instrumental leaders, if they are successful in promoting group goals, may enjoy a more distant respect.

Which of the following statements about leadership can be inferred from paragraph 2?

Read the following passage and choose the best answer for each blank.

The General Certificate of Secondary Education or the GCSE examinations for (26) _____ are the standard school-leaver qualifications taken by (27) _____ all UK students in the May and June following their 16th birthday. If you come to a UK (28) _____ school before you (29) _____ the age of 16, you will study towards GCSE examinations in up to 12 subjects. Some subjects are compulsory, including English arid mathematics, and you can select (30) _____, such as music, drama, geography and history from a series of options. GCSEs provide a good all-round education (31) _____ you can build on at college and eventually at university. AS- and A-levels are taken after GCSEs. They are the UK qualifications most (32) _____ accepted for entry to university and are available in subjects from the humanities, arts, sciences and social sciences as well as in (33) _____ subjects such as engineering, and leisure and tourism. You can study up to four subjects at (34) _____ same time for two years, (35) _____ AS-level examinations at the end of your first year (called the lower-sixth) and A-level qualifications at the end of your second year (called the upper-sixth).

(32) _____

Choose the item (A, B, C or D) that best completes each of the following sentences. 
In 1988, for the first time in British history, a National Curriculum was introduced. The National Curriculum tells pupils which subjects they have to study, what they must learn and when they have to take assessment tests. [assessment: đánh giá] 
Between the ages of 14 and 16, pupils study for their GCSE (General Certificate of Secondary Education) exams. Pupils must take English Language, Maths and Science for GCSE, as well as a half GCSE in a foreign language and Technology. addition, they must also be taught Physical Education, Religious Education and Sex Education, although they do not take exams in these subjects. 
At the age of 16, pupils can leave school. If pupils stay on, they usually take A (Advanced) levels, AS (Advanced Supplementary) level or GNVQs (Greater National Vocational Qualifications). It is quite common to combine, for example, two A levels with one AS level, or one A level with one GNVQ. 
Pupils taking A levels study traditional subjects, such as French, Physics or History. To go to university, pupils usually need two or three A levels. 
AS levels are the same standard as A levels, but only half of the content: AS level German. Pupils take the A-level German language exam, but do not take the A-level German Literature exam. 
GNVQs are vocational qualifications. Pupils usually take on GNVQ in subjects such as Business, Leisure and Tourism, Manufacturing, and Art and Design. One GVNQ (at advanced level) is equal to two A levels.

Which of the following subjects do pupils NOT take on GNVQ in? 

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
HOW TO AVOID MISCOMMUNICATION IN THE WORKPLACE
As a small-business owner, you can avoid many problems simply by improving communication in your office. By clarifying everyone's expectations and roles, you'll help to (46)............ greater trust and increase productivity among employees. Here are a few tips for doing so.
Practice active listening. The art of active listening includes (47)........ close attention to what another person is saying, then paraphrasing what you've heard and repeating it back. Concentrate (48)............ the conversation at hand and avoid unwanted interruptions (cell phone calls, others walking into your office, etc.). Take note of how your own experience and values may color your perception.
Pay attention to non-verbal cues. We don't communicate with words alone. Every conversation comes with a host of non-verbal cues -  facial  expressions,  body language,  etc.  -  that  may (49)......... contradict  what  we're saying.  Before addressing a staff member or (50).............. a project conference, think carefully about your tone of voice, how you make eye contact, and what your body is "saying." Be consistent throughout. Be clear and to the point. Don't cloud instructions or requests with irrelevant details, such as problems with past projects or issues with long-departed personnel. State what you need and what you expect. Ask, "Does anyone have any questions?" Demonstrate that you prefer questions up-front as opposed to misinterpretation later on.

(50).....................

Choose the letter A, B, C or D to complete the passage below.

"The Internet was born (1) _________scientists attempted to connect the American Defence Network to other satellite networks in (2) _________to exchange information. Soon, scientific and educational institutions as well as research departments became interested (3) _________ linking up, and, before long, the Internet had expanded into an international information and communication network.

The Internet now (4) _________ all the countries in the world. You can be connected to the Internet directly through your own computer or you can hook up to (5) _________ access system which allows you to use some of the Internet’s services."

5. You can be connected to the Internet directly through your own computer or you can hook up to (5) _________ access system which allows you to use some of the Internet’s services.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
In the early 1800s, to reach the jump-off point for the West, a family from the East of the United States could either buy a steamboat passage to Missouri for themselves, their wagons and their livestock or, as happened more often, simply pile everything into a wagon, hitch up a team, and begin their overland trek right in their front yard.
Along the macadamized roads and turnpikes east of the Missouri River, travel was comparatively fast, camping easy, and supplies plentiful. Then, in one river town or another, the neophyte emigrants would pause to lay in provisions. For outfitting purposes, the town of Independence had been preeminent ever since 1827, but the rising momentum of pioneer emigration had produced some rival jump-off points. Westport and Fort Leavenworth flourished a few miles upriver. St. Joseph had sprung up 55 miles to the northwest; in fact, emigrants who went to Missouri by riverboat could save four days on the trail by staying on the paddle wheelers to St. Joe before striking overland.
At whatever jump-off point they chose, the emigrants studied guide books and directions, asked questions of others as green as themselves, and made their final decision about outfitting. They had various, sometimes conflicting, options. For example, either pack animals or two -wheel carts or wagons could be used for the overland crossing. A family man usually chose the wagon. It was the costliest and slowest of the three, but it provided space and shelter for children and for a wife who likely as not was pregnant. Everybody knew that a top-heavy covered wagon might blow over in a prairie wind or be overturned by mountain rocks, that it might mire in river mud or sink to its hubs in desert sand, but maybe if those things happened on this trip, they would happen to someone else. Anyway, most pioneers, with their farm background, were used to wagons.

All of the following were mentioned in the passage as options for modes of transportation from the Missouri River to the West EXCEPT     .

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
On March 15, Dunes View Middle School held a contest for school bands. Student bands tried  out for the opportunity to perform at the school picnic, which will be held at the end of June. The winner of the contest was the band called Four Square. "We're very proud that we won the contest  and are excited to perform at the picnic," says Peter Zandt, who plays the guitar in the band. "And     since we hope to perform someday at other local places, like restaurants and parks, this will be  a  great first step."
The contest was the creation of music teacher Mr. Lopez and drama teacher Ms. Cho. The two thought of the idea while discussing recent years' school picnics. "The picnic is one of the biggest events of the year, but it has become a bit formulaic ," said Ms. Cho. "The activities are the same every year. We thought that a performance by a student band would make the school picnic more interesting and fun." Mr. Lopez, Ms. Cho, and three other teachers judged the contest, which took place  in the gym. Eight student bands signed up to audition. The bands varied in their musical forms: there  were several rock bands, a folk band, and even a jazz band. "I'm disappointed that my band didn't win,  but I think the judges made the right choice," says student Marisol Varga, a member of the folk trio called The Bell Girls. "Four Square is really excellent."
To see if the bands could present a wide range of musical skills, the teachers asked them  each to prepare two songs: one song with original words, and another in which students played instrumental music only. The judges finally chose the band Four Square as the winner of the contest. Four Square is a rock band with an unusual twist: it includes a violin player! The members of Four Square write their own songs and practice three times a week after school. Students and teachers agreed that the band competition was a big success. All are  looking forward  to the school picnic in June.

The word formulaic is closest in  meaning to    _.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
                     ALFRED NOBEL
Alfred Nobel was born on October 21, 1833 in Sweden. His important invention was dynamite - a powerful (1)........ _. This dynamite business made him a very rich man.
One day, Alfred Nobel read about his death in a newspaper. In fact, it was his brother's death. The mass media (2).........him a saleman of death, "The dynamite king". Nobel was very upset. He had invented dynamite to save lives - lives ( 3 )............ _ were lost because other explosives were dangerous to use. He hated violence and war. And he did not like the world to    think of him as a man of war.
He thought (4)..........the  best way for people to  use  his fortune for  years. (5)................... _  he knew  what to do with his fortune. Alfred Nobel established the Nobel Prize, an annual award to honour leaders of science, literature, and world peace. Alfred Nobel died on December 10, 1896. He was unmarried and had no children. His important decision changed the way the  world thought of him. He was remembered the way he wanted: Alfred Nobel, man of peace.

(4)..........................
 

Thank you for your purchase on September 27. Your package has shipped and is due to arrive on October 1. ---131---. Simply visit www.sprtech.com/shipping/status, enter your order number, and press “Search”.
When you receive your package, we ---132--- you to take a short survey at www.sprtech.com/survey. It is through customer feedback that we are---133---  to monitor our level of service.  Upon ---134--- of the survey, you will receive a 10% discount toward your next order.

134.............

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
                     ALFRED NOBEL
Alfred Nobel was born on October 21, 1833 in Sweden. His important invention was dynamite - a powerful (1)........ _. This dynamite business made him a very rich man.
One day, Alfred Nobel read about his death in a newspaper. In fact, it was his brother's death. The mass media (2).........him a saleman of death, "The dynamite king". Nobel was very upset. He had invented dynamite to save lives - lives ( 3 )............ _ were lost because other explosives were dangerous to use. He hated violence and war. And he did not like the world to    think of him as a man of war.
He thought (4)..........the  best way for people to  use  his fortune for  years. (5)................... _  he knew  what to do with his fortune. Alfred Nobel established the Nobel Prize, an annual award to honour leaders of science, literature, and world peace. Alfred Nobel died on December 10, 1896. He was unmarried and had no children. His important decision changed the way the  world thought of him. He was remembered the way he wanted: Alfred Nobel, man of peace.

(3)..........................
 

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.

In my experience, freshmen today are different from those I knew when I started as a counselor and professor 25 years ago. College has always been demanding both academically and socially. But students now are less mature and often not ready for the responsibility of being in college.

It is really too easy to point the finger at parents who protect their children from life’s obstacle. Parents, who handle every difficulty and every other responsibility for their children writing admission essays to picking college courses, certainly may contribute to their children’s lack of coping strategies. But we can look even more broadly to the social trends of today.

How many people do you know who are on medication to prevent anxiety or depression? The number of students who arrive at college already medicated for unwanted emotions has increased dramatically in the past 10 years. We, as a society, don’t want to “feel” anything unpleasant and we certainly don’t want our children to “suffer”.

The resulting problem is that by not experiencing negative emotions, one does not learn the necessary skills to tolerate and negotiate adversity. As a psychologist, I am well aware of the fact that some individuals suffer from depression and anxiety and can benefit from treatment, but I question the growing number of medicated adolescents today.

Our world is more stressful in general because of the current economic and political realities, but I don’t believe that the college experience itself is more intense today than that of the past 10 years. What I do think is that many students are often not prepared to be young “adults” with all the responsibilities of life.

What does this mean for college faculty and staff? We are required to assist in the basic parenting of these students – the student who complains that the professor didn’t remind her of the due date for an assignment that was clearly listed on the syllabus and the student who cheats on an assignment in spite of careful instructions about plagiarism.

As college professors, we have to explain what it means to be an independent college student before we can even begin to teach. As parents and teachers we should expect young people to meet challenges. To encourage them in this direction, we have to step back and let them fail and pick themselves up and move forward. This approach needs to begin at an early age so that college can actually be a passage to independent adulthood.

According to the writer, students’ difficulties to cope with college life are partly due to ____________.

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.
Christina and James met in college and have been dating for more than five years. For the  past two years, they have been living together in a  condo  they  purchased jointly. While Christina and James were confident in their decision to enter into a commitment like a  20-year mortgage,  they are unsure if they want to enter into marriage. The couple had many discussions about marriage and decided that it just did not seem necessary. Wasn't it only a piece of  paper? And  didn't half of all marriages end in divorce?
Neither Christina nor James had seen much success with marriage while growing up. Christina was raised by a single mother. Her parents never married, and her father has had little contact with the family since she was a toddler, Christina and her mother lived with her maternal grandmother, who often served as a surrogate parent. James grew up in  a  two-parent household  until age seven, when his parents divorced. He lived with his mother for a  few years, and then    later with his mother and her boyfriend until he left for college. James remained close with his  father who remarried and had a baby with his new wife.
Recently, Christina and James have been thinking about having children and the subject of marriage has resurfaced. Christina likes the idea of her children growing up in a traditional  family; while James is concerned about possible marital problems down the road and negative consequences for the children should that occur. When they shared these concerns with their parents, James's mom was adamant that the couple should get married. Despite having been divorced and having a live-in boyfriend of 15  years, she believes that children are better off when  their parents are married. Christina's mom believes that the couple should do whatever they want but adds that it would "be nice" if they wed. Christina and James's friends told them, married or not married; they would still be a family.

Why have Christina and James mentioned the subject of marriage again?

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks
Most Americans eat three  meals (10)...... the day: breakfast, lunch, and dinner. Breakfast begins between 7:00 and 8:00am, lunch between 11:00 am and noon, and dinner between 6:00 and 8:00 pm. On Sundays  "brunch" is  a (11) ..................of breakfast and lunch, typically beginning at 11:00 am. Students often enjoy a "study break" or evening snack around 10:00 or 11:00 pm. Breakfast and lunch tend to be light meals, with only one course. Dinner is the main meal.
For breakfast Americans will eat cereal with milk which are often mixed (12)......... in a bowl, a glass of orange juice, and toasted bread or muffin with jam, butter, or margarine. Another common breakfast meal is scrambled eggs or an omelet with potatoes and breakfast meat (bacon or sausage). People who are on a diet eat just a cup of yogurt. Lunch and dinner are more (13)............ . When eating at a formal dinner, you may be overwhelmed by the number of utensils. How do you (14)..........the difference between a salad fork, a butter fork, and a dessert fork? Most Americans do not know the answer. But knowing which fork or spoon to use first is simple: use the outermost utensils first and the utensils closest to the plate last.
(10)..............................
 

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
Because an increasing number of people are opting to work outside the traditional office, notebook PCs are becoming more and more popular. However, you should know that notebook PCs aren't for everyone. As  you (6)........ up the pros and cons of your desktop PC with a new system, you should bear (7)...........mind that you may get better profit for your money by investing in a faster, more powerful desktop PC.
Portability comes at a price. Leave your laptop unattended for any length of time in any sort of public place and you will quickly discover that it has been stolen. You could even lose it without any intentional neglect on your area; laptops (and all the business and personal information they  contain)  are easy (8)..... for skilled thieves. So, yes, there are definitely serious security issues. Also, if you are prone to tossing your laptop around as you do your purse, workout bag or umbrella, you'll probably break it before you get your money's worth. Guarantees are getting better and longer, but they still won‘t cover a simple slip, let alone (9)........ carelessness. So, before you (10) ........ out to get yourself the latest technological appliance, think long and hard as to whether a notebook PC is really suitable for you.
(10)..............................

Often the craft worker’s place of employment in ancient Greece was set in rural isolation. Potter, for instance, found it convenient to locate their workshops near their source of clay, regardless of its relation to the center of settlement, At Corinth and Athens, however, two of the best-known potters’ quarters were situated on the cities’ outskirts, and potters and makers of terra-cotta figurines were also established well within the city of Athens itself. The techniques of pottery manufacture had evolved well before the Greek period, but marked stylistic developments occurred in shape and in decoration, for example, in the interplay of black and other glazes with the red surface of the fired pot. Athenian black-figure and red- figure decoration, which emphasized human figures rather than animal images, was adopted between 630 and 530 B.C.; its distinctive color and luster were the result of the skillful adjustments of the kiln’s temperature during an extended three-stage period if firing the clayware. Whether it was the potters or the vase-painters who initiated changes in firing is unclear; the functions of making and decorating were usually divided between them, but neither group can have been so specialized that they did not share in the concerns of the other.

The broad utility of terra-cotta was such that workers in clay could generally afford to confine themselves to either decorated housewares like cooking pots and jars or building materials like roof tiles and drainpipes. Some sixth-and fifth-century B.C. Athenian pottery establishments are known to have concentrated on a limited range of fine ware, but a rural pottery establishment on the island of Tliasos produced many types of pottery and roof tiles too, presumably to meet local demand. Molds were used to create particular effects for some products, such as relief-decorated vessels and figurines; for other products such as roof tiles, which were needed in some quantity, they were used to facilitate mass production. There were also a number of poor-quality figurines and painted pots produced in quantity by easy, inexpensive means- as numerous featureless statuettes and unattractive cases testify.

The passage mainly discusses ancient Greek pottery and its     .

Choose the best answer:
They __________ the project “Environmental preservation” at this time next Tuesday.

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions:
Environmental pollution is one of the impacts of human activities on the Earth. Pollution occurs when pollutants contaminate the natural surroundings; which brings about changes that affect our normal lifestyles adversely. Pollution disturbs our ecosystem and the balance in the environment. Pollution occurs in different forms; air, water, soil, radioactive, noise, heat/ thermal and light Let us discuss the causes and effects of air pollution on mankind and the environment as a whole.
Air pollution is the most prominent and dangerous form of pollution. It occurs due to many reasons. Excessive burning of fuel which is a necessity of our daily lives for cooking, driving and other industrial activities; releases a huge amount of chemical substances in the air every day; these pollute the air. Smoke from chimneys, factories, vehicles or burning of wood basically occurs due to coal burning; this releases sulphur dioxide into the air making it toxic.
The effects of air pollution are evident too. The increase in the amount of CO2 in the atmosphere leads to smog which can restrict sunlight from reaching the earth. Thus, preventing plants in the process of photosynthesis. Gases like sulfur dioxide (SO2) and nitrogen oxide (NO) can cause acid rain.
The decrease in quality of air leads to several respiratory problems including asthma or lung cancer. Chest pain, congestion, throat inflammation, cardiovascular disease, respiratory disease are some of diseases that can be caused by air pollution.
The emission of greenhouse gases particularly CO2 is leading to global warming. Every other day new industries are being set up, new vehicles come on roads and trees are cut to make way for new homes. All of them, in direct or indirect way lead to increase in CO2 in the environment. The increase in CO2 leads to melting of polar ice caps which increases the sea level and pose danger for the people living near coastal areas.
Ozone layer is the thin shield high up in the sky that stops ultra violet rays from reaching the  earth. As a result of human activities, chemicals, such as chlorofluorocarbons (CFCs), were released into the atmosphere which contributed to the depletion of ozone layer.

According to the passage, which of the following sentences is NOT true?

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
Generally, in order to be preserved in the fossil record, organisms must possess hard body parts such as shells or bones. Soft, fleshy structures are quickly destroyed by predators or decayed by bacteria. Even hard parts left on the surface for any length of time will be destroyed, therefore, organisms must be buried rapidly to escape destruction by the elements and to be protected against agents of weathering and erosion. Marine organisms thus are better candidates for fossilization than those living on the land because the ocean is typical the site of sedimentation, whereas the land is largely the site of erosion. The beds of ancient lakes were also excellent sites for rapid burial of skeletal remains of freshwater organisms and skeletons of other animals, including those of early humans, Ancient swaps were  particularly plentiful with prolific growths of vegetation, which fossilized in abundance. Many animals became trapped in bogs overgrown by vegetation. The environment of the swaps kept bacterial decay to a minimum, which greatly aided in the preservation of plants and animals. The rapidly accumulating sediments in flood plains, deltas, and stream channels buried freshwater organisms, along with other plants and animals that happened to fall into the water.
Only a small traction of all the organisms that have ever lived are preserved as fossils. Normally, the remains of a plant or animal are completely destroyed through predation and decay. Although it seems that fossilization is common for some organisms, for others it is almost impossible. For the most part of, the remains of organisms are recycled in the earth, which is fortunate because otherwise soil and water would soon became depleted of essential nutrients. Also, most of the fossils exposed on Earth’s surface are destroyed by weathering processes. This make for an incomplete fossil record with poor or no representation of certain species. The best fossils are those composed of that form the vast majority of unaltered fossils. Calcite and aragonite also contributed to a substantial number of fossils of certain organisms.

According to the passage, an organisms without hard body parts     

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrases that best fits each of the numbered blanks.
When I was at school, sports day was the highlight of the year. Let me set the scene. First of all, on sports day, it  was  always  bound (1)...... rain. Sunny weather? No such luck. Despite the previous two months of soaring temperatures, as likely as not, on the morning of the games, The temperature  would plummet. So, imagine  a hundred (2)........ small children, dressed in tight shorts and thin vests, shivering in the cold, unaware of the heartbreak that lies in store for them. Swept up by the excitement and desperate to win, tempers soon get frayed. One girl finds herself disqualified from the egg and spoon race despite giving it everything she’s got, and another boy, (3)......... jealous of the winner of the sack race, makes the mistake of being rude to him within earshot of the teachers. Scores of tiny children, bitterly disappointed at tasting defeat for the first time, break down and cry. Twenty years on, I’m certainly not (4)......... any young, but I do have some really lasting (5)............. _of those days at school!
(4)...........................

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.
                     ALFRED NOBEL
Alfred Nobel was born on October 21, 1833 in Sweden. His important invention was dynamite - a powerful (1)........ _. This dynamite business made him a very rich man.
One day, Alfred Nobel read about his death in a newspaper. In fact, it was his brother's death. The mass media (2).........him a saleman of death, "The dynamite king". Nobel was very upset. He had invented dynamite to save lives - lives ( 3 )............ _ were lost because other explosives were dangerous to use. He hated violence and war. And he did not like the world to    think of him as a man of war.
He thought (4)..........the  best way for people to  use  his fortune for  years. (5)................... _  he knew  what to do with his fortune. Alfred Nobel established the Nobel Prize, an annual award to honour leaders of science, literature, and world peace. Alfred Nobel died on December 10, 1896. He was unmarried and had no children. His important decision changed the way the  world thought of him. He was remembered the way he wanted: Alfred Nobel, man of peace.

(5)..........................
 

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions:
During the second half of the nineteenth century, the production of food and feed crops in the United States rose at an extraordinarily rapid rate. Com production increased by four and a half times, hay by five times, oats and wheat by seven times. The most crucial factor behind this phenomenal upsurge in productivity was the widespread adoption of labor-saving machinery by northern farmers. By 1850 horse- drawn reaping machines that cut grain were being introduced into the major grain-growing regions of the country. Horse-powered threshing machines to separate the seeds from the plants were already in general use. However, it was the onset of the Civil War in 1861 that provided the great stimulus for the mechanization of northern agriculture. With much of the labor force inducted into the army and with grain prices on the rise, northern farmers rushed to avail themselves of the new labor-saving equipment. In 1860 there were approximately 80,000 reapers in the country; five years later there were 350,000.
After the close of the war in 1865, machinery became ever more important in northern agriculture, and improved equipment was continually introduced. By 1880 a self-binding reaper had been perfected that not only cut the grain, but also gathered the stalks and bound them with twine. Threshing machines were also being improved and enlarged, and after 1870 they were increasingly powered by steam engines rather than by horses. Since steam-powered threshing machines were costly items-running from $ 1,000 to $4,000 - they were usually owned by custom thresher owners who then worked their way from farm to farm during the harvest season. “Combines” were also coming into use on the great wheat ranches in California and the Pacific Northwest. These ponderous machines - sometimes pulled by as many as 40 horses - reaped the grain, threshed it, and bagged it, all in one simultaneous operation.
The adoption of labor-saving machinery had a profound effect upon the sale of agricultural operations in the northern states-allowing farmers to increase vastly their crop acreage. By the end of century, a farmer employing the new machinery could plant and harvest two and half times as much com as a farmer had using hand methods 50 years before.

The word “they” in paragraph 2 refers to     .