Every year more and more plants and animals disappear and they will never to be seen again．Strangely, it is the most intelligent but most thoughtless animal that is causing most of the problems－man．Nature is very carefully balanced and if this balance is disturbed, animals can disappear alarmingly fast．Every day, thousands of species of animals draw closer to extinction．There are countless numbers of species which may become extinct before they are even discovered．
In many lakes the fish are dying．Fishermen are worried because every year there are fewer fish and some lakes have no fish at all．Scientists are beginning to get worried too．What is killing the fish?
The problem is acid rain．Acid rain is a kind of air pollution．It is caused by factories that burn coal, oil or gas．These factories send smoke high into the air．The wind often carries the smoke far from the factories．Some of the harmful substances in the smoke may come down with the rain hundreds of miles away．The rain in many places isn't natural and clean any more．It's full of acid chemicals．When it falls in lakes, it changes them too．The lakes become more acidic．Acid water is like vinegar or lemon juice．It hurts when it gets in your eyes．It also kills the plants and animals that usually live in lake water．That is why the fish are dying in lakes．
But dead fish may be just the beginning of the problem．Scientists are finding other effects of acid rain．In some large areas trees are dying．Not just one tree here and there, but whole forests．At first scientists couldn't understand why．There were no bugs or diseases in these trees．The weather was not dry．But now they think that the rain was the cause．Acid rain is making the earth more acidic in these areas．Some kinds of trees cannot live in the soil that is very acidic．
Now scientists are also beginning to study the effects of acid rain on larger animals．For example, they believe that some deer in Poland are less healthy because of acid rain．If deer are hurt by the rain, what about people?This is the question many people are beginning to ask．No one knows the answer yet．But it is an important question for us all．
(1)
Scientists think acid rain ________．
[ ]
A．
is killing people
B．
helps kill bugs
C．
is killing trees
D．
fertilizes the soil
(2)
What happens to thousands of species of animals every year?
[ ]
A．
People hunt for their meat．
B．
They die out on the earth．
C．
Most of them starve to death in the winter．
D．
They had to migrate to other places．
(3)
Which of the following is true?
[ ]
A．
Dead fish in lakes is the only problem caused by acid rain．
B．
If we don't make an attempt to stop acid rain, we may never see some animals again．
C．
Scientists are sure that acid rain is not harmful to mankind．
D．
There's no reason to worry about several trees that died of some unknown disease．
(4)
What is NOT mentioned in the text?
[ ]
A．
Coal, oil or gas form dangerous combinations after being burnt．
B．
Fish are unable to live in the water containing acidic chemicals．
C．
Acid rain is capable of dissolving some rocks and stones．
D．
If some animals can be affected by acid rain, people may be in danger．