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

• What is the passage mainly about?

• Which of the following is NOT the thing Bethan does as a Facebook addict?

• What does the author probably mean by using the expression “children interrupt their education to go to school” (lines 2-3) ?

ZUNIA12

• “Bricks” are mentioned in paragraph 3 to indicate how _______.

• Which of the following do music arrangers probably NOT do?

• What does the passage mainly discuss?

•  The word “metamorphosis” in paragraph 2 is closest in meaning to ................

• What causes dodder to grow in a particular direction?

• It can be inferred from the passage that the author is ___________.

• Why does the author mention “artistic, political, or pedagogic communication” in the passage?

• The word “fragile” in paragraph 4 is closest in meaning to .........

• The paragraph following the passage most likely discusses:

• According to the passage, an overconfident front may hide _______.

• It can be inferred from the passage that brain size is assumed to ___________.

• According to the passage, all of the following have caused damage to the paintings EXCEPT ………………...

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

•  The word “ them” which is bold and italic refers to ___________.

• This reading would most probably be assigned in which of the following courses?

• According to the passage, the difficulty in diagnosing allergies to foods is due to ___________.

• Which of the following is NOT true about algae?