题目内容：

In the 1960s Professor Bolin predicted that the “greenhouse effect”, caused by an increase in the amount of carbon dioxide (CO₂) in the atmosphere, would lead to important changes in the Earth’s climate. At the time his prediction were regarded as science fiction. But it is now gradually agreed that the amount of carbon dioxide in the atmosphere will double from 0.03% to 0.06% in the next 50 years and that temperatures worldwide will rise by 2°Celsius.

Although a temperature rise of 2°may not seem significant, the local effects may be much greater: in polar regions a rise of 10°by 2025 is expected and in Northern Europe a rise of 4°. Indeed the first effects were expected to be felt before the end of the 20^th century,

But how does the “greenhouse effect”operate and why should such a tiny proportion（比例）of CO₂ have such a harmful effect? When living creatures breathe out or when things are burned, CO₂ enters the atmosphere. Until recently all of this was absorbed by plants, which converted it back into oxygen.

However, the balance of nature has been disturbed. In power stations, in factories and in our cars, we are burning more and more fossil fuels( coal, oil and natural gas ) and this produces huge quantities of CO₂---18 billion tons of it enter the atmosphere every year. Added to this, the destruction of forests means that less CO₂ can be converted into oxygen by plants. So, the amount of CO₂ in the atmosphere is increasing every year.

1.Which of the following statements is true according to the passage?

A．Professor Bolin’s predictions were taken seriously in the first place

B．Only a small portion of the atmosphere consists of carbon dioxide

C．No changes in climate will become noticeable for 50 years or more

D．The rise in temperature will probably be 2 degrees in every part of the world.

2.The amount of CO₂ in the atmosphere is increasing every year because       .

A．Carbon dioxide is produced when we breathe

B．Carbon dioxide is produced when we burn things

C．More forests are destroyed and more fossil fuels are burned

D．The global temperature keeps rising

3.The “greenhouse effect”refers to         

A．the problem of the rising global temperature

B．the problem of increasing population worldwide

C．the problem of decreasing population worldwide

D．the problem of air pollution

4.The underlined word“operate”in the third paragraph most probably means“      ”.

A．play

B．move

C．manage

D．function