题目内容：

Although the weathermen’s forecasts for a month ahead are only little better than guesswork, they are now making long-term forecasts into the next century with growing confidence. The main trend in the world’s climate in the coming years will, scientists say, be a predictable result of man’s activities.

At the start of the industrial revolution nearly two centuries ago, man set off a big experiment in planetary engineering. Unaware of what he was doing, he spared no thought for the consequences. Today the possible outcome is alarmingly clear, but the experiment is unstoppable. Within the lifetime of many of us, the Earth may become warmer than it has been for a thousand years. By the middle of this century it may be warmer than it has been since the last Ice Age.

A warmer climate may seem welcome, but it could bring many dangers： damages to crops in the world’s main food-producing areas, famine(饥荒),  economic instability, civil unrest and even war.

In the much longer term, melting of the great ice-caps of Greenland and Antarctica could raise sea-levels throughout the world. The average sea-level has already risen a foot since the turn of the last century, and if the ice-caps disappear completely, it would rise by nearly 200 feet. Complete melting might take many centuries, but even a small increase in sea-level would threaten low-lying parts of the world such as the Netherlands.

44. Long-term weather forecasts beyond the year 2050 may seem strange because ____.

A. none of us will be alive then

B. weathermen can even forecast next month’s weather correctly

C. weathermen can forecast much better than they used to

D. no one can stop engineering experiments

45. Weathermen believe that our future climate will be the direct result of ____.

A. the big scientific experiment       B. clever long-term forecasts

C. the melting of the ice-caps          D. planets changing course

46. One of the results of a warmer world climate could be ____.

A. an increase in food production

B. greater co-operation between countries

C. the death of millions of people from starvation

D. a reduction in the amount of oil we use

47. Scientists are fairly sure that by the year 2050, _______.

A. the sea-level will have risen obviously

B. there will have been the Third World War

C. most countries will have been flooded

D. the polar ice-caps will have melted completely