As a result of pollution, Lake Erie, on the borders of the USA and Canada, is no

As a result of pollution, Lake Erie, on the borders ofthe USA and Canada, is now without many living things.

   Pollution in water is not simply a matterof “poisons” killinglarge numbers of fish overnight. Very often the effects of pollution are notnoticed for many months or years because the first organisms (生物体) to be affected are either plants or plankton (浮游生物). These organisms are the food of fish, birds, andother creatures. When this food disappears, the fish and birds die too. In thisway a whole food chain can be wiped out, and it is not until dead fish andwater birds are seen at the river’s edge or onthe sea shore that people realize what is happening.

   Where do the substances which pollutewater come from? There are two main sources, sewage(污水) and industrial waste. As more detergent (洗涤剂)is used in homes, more of it is finally put into ourrivers, lakes and seas.  Detergents harm water birds by breaking down thenatural substances which keep their feathers waterproof. Sewage itself,if not properly treated, makes the water dirty and prevents all forms of lifein rivers and the sea from receiving the oxygen they need. Industrial waste iseven more harmful since there are many highly poisonous materials in it, suchas copper and lead.

   So if we want to stop this pollution, theanswer is simple. Sewage and industrial waste must be made clean before flowinginto the water reservoirs. It may already be too late to save some rivers andlakes, but others can still be saved if the correct action is taken at once.

1.Pollution in water is noticed ________.

A. when the first organisms are affected

B. when many fish and birds die   

C. when poisons are poured into water

D. As soon as the balance of nature is destroyed

2.Living things die in a lake or river because thereis no ________.

A.water         B.fish                  C.Poison              D. oxygen

3.The underlined word “waterproof” in the thirdparagraph means “          ”.

A. full of water   B. not allowing water togo through

C. covered with water   D. cleaned by water

4.Which of the following things is /are harmfulaccording to the passage？

A. Industrial waste and chemicals    B.Water in the river

C. Coal and wood  D. plastic

试题答案

【答案】

1.B

2.D

3.B

4.A

【解析】

试题