As a result of pollution, Lake Erie, on the borders of the USA and Canada, is now without any living things. Pollutions in water are not simply a matter of “poisons” killing large numbers of fish overnight. Very often the effects of pollution are not noticed for many months or years because the first organisms to be affected are either plants or plankton. But these organisms are the food of fish and birds and other creatures. When this food disappears, the fish and birds die in this way a whole food chain can be wiped out, and it is not until dead fish and water birds are seen at the river’s edge or on the sea shore that people realize what is happening. Where do the substances which pollute the water come from? There are two main sources – sewage and industrial waste. As more detergent is used in the home, so more of it is finally put into our rivers, lakes and seas. Detergents harm water birds dissolving the natural substance which keep their feather waterproof. Sewage itself, if it is not properly treated, makes the water dirty and prevents all forms of life in rivers and the sea from receiving the oxygen they need. Industrial waste is even more harmful since there are many high poisonous things in it, such as copper and lead. So, if we want to stop this pollution, the answer is simple, sewage and industrial waste must be made clean before flowing into the water. It may already be too late to save some rivers and lakes, but others can still be saved if the correct action is taken at once.

The living things die because there is no ............ in the lake or river.

Câu hỏi liên quan

• What does the author imply in the last sentence of the passage?

• According to the passage, the study of learning is important in many fields due to ______.

• The expression “is based on” in the first paragraph could be best replaced by ..............

ZUNIA12

• In the passage, the author gives the explanation of the concept of mandatory volunteer programs by ______.

• The word “checked” in the second paragraph is closest in meaning to ______.

• What might be the most suitable title for this reading passage?

• In line 1, the author uses the words “human assistance” to mean ............

• According to the passage, all of the followings are TRUE except ___________.

• The expression “ keep tabs on” is closest meaning to ___________.

• It can be inferred from the passage that the previous passage probably discussed ________.

• The word “reluctant” in the third paragraph can best be replaced by ............

• The writer seems to imply that Europeans travel mostly for the reason that ...............

• What is NOT true about the passage?

• The word “they” in bold in paragraph 2 refers to ...............

• What did researchers discover in the study of honeybees discussed in paragraph 2?

• The word "These" in paragraph 3 refers to ..........

• Students who continue studying at university after having graduated are called .........

• The word “tolls” in paragraph 4 is closest in meaning to which of the following?

• What does the word magni stand for?

• Why does the author mention spaghetti?