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

• The writer says that when he was very young ________.

• According to the passage, what can be learnt about passive students?

• Of the animals with backbones, the first to appear were ______

ZUNIA12

• The word "discrete" in line 16 is closest in meaning to ......

• When she decided to give up Facebook ..............

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

• According to the passage, what does a constricted and harsh voice indicate?

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

• Where did Marianne Moore grow up?

• Which of the following is NOT true?

• What does the writer’s mother look like?

• The word “they” in paragraph 3 refers to ___________.

• All activities mentioned in the passage are household chores EXCEPT .................

• Which of the following would NOT be a problem for the construction plan?

• What does the author say in paragraph 1 regarding most species in Earth’s history?

• It can be inferred from the passage that ___________.

• The word "innovative" in line 1 could best be replaced by ...............

• What does “they” refer to?

• The word neighboring would BEST be replaced with ............

• According to the passage, which of the following is NOT true about a logrolling?