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.

What is the meaning of “waterproof” in the second paragraph?

Câu hỏi liên quan

• Which of the following sentences is true?

• The price of a computer is now _____________

• The main difficulty with organ transplants is .............

ZUNIA12

• According to the passage, to learn new information, low-achieving students do NOT .............

• With what topic does this passage primarily deal?

• According to paragraph 1, which of the following is NOT true?

• What is the main idea of the passage?

• According to the passage, Charlotte Taylor believes that women in 1970s ___________

• People thought Merlin was a dreamer because he__________.

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

• According to the author, one mark of a civilized society is that if ..............

• The phrase “these years” in the third paragraph refers to ________.

• Which of the following statement is TRUE about the passage?

• M.L. was ................. by the atmosphere in which he grew up.

• Based on the passage, what is probably true about tsunamis?

• This article is about ................

• It can be inferred from the passage that the principal cause of California’s population surge between 1940 and 1950 was ..........

• Why are there white rings on each end of the football?

• The word “vital” in paragraph 2 is closest in meaning to______

• Who is intended to benefit from the advice given in the article?