The ability to conduct electricity is one of the key properties of a metal. Other solid material such as silicon can conduct electricity but only effectively at certain temperatures. Also, some substances such as salt (sodium chloride) can conduct when molten or when dissolved in water. The ability of metals to conduct electricity is due to how their atoms bond together. In order to bond together the metal atoms lose at least one of their outermost electrons. This leaves the metal atoms with a positive charge and they are now strictly ions. The lost electrons are free to move in what are known as a sea of electrons. Since the electrons are negatively charged they attract the ions and this is what keeps the structure together.

An electric current is a flow of charge and since the electrons in the sea of electrons are free to move they can be made to flow in one direction when a source of electrical energy such as a battery is connected to the metal. Hence we have an electric current flowing through the wire, and this is what makes metals such good conductors of electricity. The only other common solid conducting material that pencil users are likely to encounter is graphite (what the 'lead' of a pencil is made from). Graphite is a form of carbon and again the carbon atoms bond in such a way that there is a sea of electrons that can be made to flow as an electric current. Likewise, if we have an ionic substance like salt we can make the electrically charged ions flow to create a current but only when those ions are free to move, either when the substance is a liquid or dissolved in water. In its solid state an ionic substance like salt cannot conduct electricity as its charged ions cannot flow.

Electrical insulators are substances that cannot conduct electricity well either, because they contain no charged particles or any charged particles they might contain do not flow easily. Water itself is a poor conductor or electricity as it does not contain a significant amount of fully charged particles (the ends of a water molecule are partly charged but overall the molecule is neutral). However, most water we encounter does contain dissolved charged particles, so it will be more conductive than pure water. Many of the problems that occur when touching electrical devices with wet hands result from the ever-present salt that is left on our skin through perspiration and it dissolves in the water to make it more conductive.

The word "they” in paragraph 3 refers to.

Choose the best answer:
been to/ is/ What/ destination/ exciting/ you/ have/ the most?

Read the following passage and choose the best answer (A, B, C, D):
Carbohydrates, which are sugars, are an essential part of a healthy diet. They provide the main source of energy for the body, and they also function to flavor and sweeten foods. Carbohydrates range from simple sugars like glucose to complex sugars such as amylose and amylopectin. Nutritionists estimate that carbohydrates should make up about one-fourth to one-fifth of a person's diet. This translates to about 75- 100 grams of carbohydrates per day. A diet that is deficient in carbohydrates can have an adverse effect on a person's health. When the body lacks a sufficient amount of carbohydrates it must then use its protein supplies for energy, a process called gluconeogenesis. This, however, results in a lack of necessary protein, and further health difficulties may occur. A lack of carbohydrates can also lead to ketosis, a buildup of ketones in the body that causes fatigue, lethargy, and bad breath.
1. What is the main idea of this passage?

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They couldn’t pass the final ____________.

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We do not ……………. away anything useful.

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:
Animals have an intuitive awareness of quantities. They know without analysis the difference between a number of objects and a smaller number. In his book "The Natural History of Selboure" (1786), the naturalist Gilbert White tells how he surreptitiously removed one egg a day from a plover's nest, and how the mother laid another egg each day to make up for the missing one. He noted that other species of birds ignore the absence of a single egg but abandon their nest if more than one egg has been removed. It has also been noted by naturalists that a certain type of wasp always provides five - never four, never six - caterpillars for each of their eggs so that their young have something to eat when the eggs hatch. Research has also shown that both mice and pigeons can be taught to distinguish between odd and even numbers of food pieces.
These and similar accounts have led some people to infer that creatures other than humans can actually count. They also point to dogs that have been taught to respond to numerical questions with the correct number of banks, or to horses that seem to solve arithmetic problems by stomping their hooves the proper number of times.
Animals respond to quantities only when they are connected to survival as a species - as in the case of the eggs - or survival as individuals - as in the case of food. There is no transfer to other situations of from concrete reality to the abstract notion of numbers. Animals can "count" only when the objects are present and only when the numbers involved are small - not more than seven or eight. In lab experiments, animals trained to "count" one kind of object were unable to count any other type. The object, not the numbers, are what interest them. Animals' admittedly remarkable achievements simply do not amount to evidence of counting, nor do they reveal more than innate instincts, refined by the genes of successive generations, or the results of clever, careful conditioning by trainers.

Why does the author refer to Gilbert White's book in line 2?

Mark the letter A, B, C, or D to indicate the sentence that best combines each pair of sentences in the following questions.
He became successful as a professional writer at the age of 20.

Rewrite the sentence
Mr. Peter drives to Amsterdam every month.

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This area is ________ overcrowding that the price of housing goes up very high.

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They noticed him .......................... the agreement. 

Read the reading below carefully, and then complete it with the best option A, B, C or D given below:
Joanne Rowling became famous almost overnight. She is the (1)_____of a highly successful series of books for young people. Joanne has dreamt of being a writer for as long as she can remember. In fact, she has been(2)_____ stories and characters ever since she was a schoolgirl. When she was still quite young, the family moved to a town called Chepstow. A family who lived (3) ____were called Potter, and she used their name for the hero of her books. She and her sister, Di, (4)_____a state school in town. At school, she was hard-­‐working and rather reserved. She was (5)_____good at English and languages. Her talent for telling stories made her popular figure in the school. During breaks between (6) _____she was often surrounded by a crowd of friends, excited to hear the (7) _____story she had written. She often included her classmates in her stories though they were not always aware of this! When she left school, Joanne succeeded in getting a place at university. After graduating, she got a(8) _____in French. Then Joanne started to work as a teacher in a school in Portugal. She married a journalist but, sadly, the couple soon (9)_____and she moved to Edinburgh. She had (10) _____and couldn’t even afford a plastic folder to send her new book to potential publishers. However, one wonderful day a publisher said “yes”. It was the greatest day of her life

Surely there are now reasons why (1)____ book ought to be dead, or at least very badly injured. If so, why does it not show proper respect for these reportedly less literate times (2)_____ die out? There is clearly more than a single answer to this question. Firstly, we have more leisure time than we (3)______ to, and people are generally living longer, which means there is more time to do more (including reading books). As (4)______ as this, there is the strength of the book as a tradition. We are all too dismissive of traditions in our modern world, but they can have very strong pull (5)_____ us.

(70)_________

Read the passage below carefully, and then choose the best answer:
Flying Drones into Danger Zones
A plane is sent deep into the enemy territory with a deadly mission. It is assigned to eliminate several key targets with a precision bombing campaign. This mission won’t be easy, however, as to be successful, the plane will have to avoid enemy rockets and tank fire. There will be no risk to the life of the “pilot” of the plane because he will not be able to aboard the vessel. Instead, he will be thousands of miles away inside a control tower, as he is operating a drone. Drones, which are also called UVAs or unmanned aerial vehicles, marked a major step forward in technology. Inventors have been working on them since the early 1900s. Although some devices were designed back then, they weren’t able to do much more than a standard model airplane. In fact, it was not until a US plane was shot down in 1959 during the Cold War that the US military really got serious about drones. The aim was to save pilots’ lives while flying over hazardous territories. Drones usually fall into two categories. The first type of drones relies on human control from a remote location. The second type of drones is pre­programmed with computer instructions, and it then completes its mission operating autonomously. In addition to protecting pilots’ lives, drones also have several other advantages. They can stay in the air for longer periods of time because there is no concern for eating, sleeping, or rest breaks that pilots typically require. Drones can also be produced cheaper since manufacturers don’t need to value safety precautions as they would for aircraft flown by humans. Despite their usefulness, military drones have been the cause of great criticism over the past decade. There have been cases of British and American drones missing their targets and killing innocent civilians instead. The Brookings Institution released a statistic that for every military leader who is killed by a drone strike, ten civilians die. Some suggest that if human pilots were flying these planes, they wouldn’t have made these errors. Drones don’t always have targets that they must eliminate. The military also employs special surveillance drones that use long-range cameras to gather information about buildings, enemy soldier formations, and other vital information from the ground. In the end, whether people are for or against the use of drones, it appears that they are certain here to stay.
2. What happened in 1959?

Read the passage carefully and choose the correct answer.

Jean spent her first few years in Hooper and her family moved to Otsego early in her life. She was only ten when her father died unexpectedly, leaving her mother to raise and support their family alone. Her mother soon went to work outside the home to provide for the family, and Jean, being one of the oldest, had to help care for her younger siblings. Although she had much responsibility at home, Jean thoroughly enjoyed school and was an excellent student. She went on to graduate 10th in her class at Otsego High School in 1953.

While still in high school, Jean met a young man named Charles "Chuck" Holly, at a dance in Alamo; and they were quite taken with each other. Over the next few years, their love for each other blossomed and they were married on February 24, 1953, while Jean was still in school. At the time, Chuck was serving his country in the military, and had come home on leave to marry his sweetheart. Unfortunately, shortly thereafter, he was sent overseas to serve in Korea for the next fifteen months.

Upon his discharge, the couple settled into married life together in the Plainwell, Otsego area. To help make ends meet, Jean went to work at the collection bureau in Kalamazoo for a while, before taking a job at the cheese company in Otsego. In 1964, Chuck and Jean were overjoyed with the birth of their son, Chuck, who brought great joy into their lives. Jean remembered how her mother was always gone so much working after her father died and she did not want that for her son, so she left her job to devote herself to the role of a mother.

Jean _______.

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The first/ sport competition/ held/ Greece/ 776 B.C.

We are working, that means that we are contributing goods and services to our society.

(tìm lỗi sai )
(285)_______

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There is no ______that he has been here.

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I detest ___________ with weird people.

Some researchers have just _____ a survey of young people s points of view on contractual marriage.
(167)______

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Carlos was ………. the first prize in the essay competition.

Rewrite the sentence
We/ before/ seen/ have/ Physical/ never/ this/ experiment.