题目内容
A In the atmosphere,carbon dioxide allows the sun's rays to enter but prevents the heat from escaping. According to a weather expert's prediction,the atmosphere will be warmer in the year 2050 than it is today,if man continues to burn fuels at the present rate. If this war?ming up took place,the ice caps in the poles would begin to melt,thus raising sea level several metres and severely flooding coastal cities. Also,the increase in at?mospheric temperature would lead to great changes in the climate of the northern hemisphere.
In the past,concern about manmade warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet. But the weather experts are now paying more attention to West Antarctica,which may be affected by only a few degrees of warming,in other words,by warming on the scale that will possibly take place in the next fifty years from the burning of fuels. Satellite pictures show that large areas of Antarctic ice are already disappea?ring. The evidence suggests that warming has taken place. This fits the theory that carbon dioxide warms the earth.
However,most of the fuel is burnt in the northern part of the earth,where temperatures seem to be falling. Scientists conclude,therefore,that up to now natural influences on the weather have exceeded those caused by man. The question is：Which natural cause has most effect on the weather?
One possibility is the behaviour of the sun. Astronomers at one research sta?tion have studied the hot spots and cold spots,that is,the relatively less hot spots,on the sun. This seems to have a greater effect on the distribution of the earth's at?mospheric pressure,and consequently on wind circulation (循环) .The sun is also variable (可变的) over a long term. Its heat output (输出) goes up and down in cycles. The latest trend being downward is on the way. But that is only an imagination.
1. The carbon dioxide in the atmosphere would .
A. prevent the sun's rays from reaching the earth's surface
B. mean warming up in the Arctic
C. account for great changes in the climate
D. raise the temperature of the earth's surface
2. The article is written to explain ,
A. the greenhouse effect
B. the solar effects on the earth
C. the solar weather
D. the causes affecting weather
3. Although the fuel is greater in the northern part,temperatures there seem to be falling. This is .
A. mainly because the carbon dioxide is rising
B. possibly because the ice caps in the poles are melting
C. due to the effect of the earth's climate
D. partly due to the activity of the sun
4. What does the underlined word "exceeded" in Paragraph 3 mean?
A. To be the same as. B. To be slower than.
C. To be better than. D. To be bigger than.
本文主要讨论了人类大量排放二氧化碳到大气中，造成了气候变暖，但是在北半球气候却变冷的原因。
1. D细节理解题。文章第一段讲到二氧化碳在大气中就像温室的玻璃屋顶一样吸收太阳的光线并阻挡光热的流失，文章第二段最后一句话又再次提到二氧化碳能使地球变暖的理论。因此正确答案为D项。
2. D写作意图题。全文讲述的是影响天气的诸多原因。选项A、B、C在文中均被提及但不足以概括全文的主旨，只有D 项是比较全面的。
3. D细节理解题。文章第三段提及这一现象时讲到，科学家们认为：这一现象的产生是因为到目前为止自然界对天气的影响要大于人类对天气的影响。而究竟是哪种自然力量对天气的影响最大呢？文章第四段第一句给出了答案：其中一个可能就是太阳活动。
D项与此意相符。
4. D词义猜测题。根据最后一段的"This seems to have a greater effect on the distribution of the earth's atmospheric pressure,and consequently on wind circulation (循环) ."可知，自然界对天气的影响要大于人类对天气的影响。
