生态金字塔特指能量金字塔，其次还有（）和数目金字塔。

In the atmosphere, carbon dioxide acts rather like a one-way mirror or the glass in the roof of a greenhouse which allows the sun's rays to enter but prevents the heat from escaping.

　　 According to a weather expert' s prediction, the atmosphere will be 3℃ warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming 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 atmospheric temperature would lead to great changes in the climate of the northern hemisphere (北半球), possibly resulting in an alteration of the earth's chief food growing zones.

　　  In the past, concern about a man-made 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 Antarctic, which may be affected by only a few degrees of warming, in other words, by a 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 disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth.

　　  However, most of the fuel is burnt in the northern hemisphere, where temperatures seem to be falling. Scientists conclude , therefore, that up to now natural influences on the weather have gone beyond those caused by man. The question is: Which natural cause has most effect on the weather?

　　  One possibility is the variable behavior of the sun. Astronomers at one research station have studied the hot spots and "cold" spots (that is, the relatively less hot spots) on the sun. As the sun rotates (使旋转), every 27. 5 days, it presents hotter or "colder" faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the earth's atmospheric pressure, and consequently on wind circulation. The sun is also changeable over a long term: its heat output goes up and down in cycles, the latest trend being downward.

　　  Scientists are now finding shared relations between models of solar weather interactions and the actual climate over many thousands of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia (惯性) of the earth's climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful opposed balance to the sun's fading heat .

66. It can be concluded that a concentration of carbon dioxide in the atmosphere would_________.

A. mean a warming-up in the Antarctic

B. raise the temperature of the earth' s surface

C. prevent the sun's rays from reaching the earth's surface

D. explain the cause of  great changes in the climate in the northern hemisphere

67.The article was written to explain ___________. 

A. the greenhouse effect

B. the solar effects on the earth

C. the causes affecting weather

D. the models of solar-weather interactions

68. Although the fuel consumption is greater in the northern hemisphere, temperatures there　seem to be falling. This is__________.

A. mainly because the levels of carbon dioxide are rising

B. partly due to changes in the output of solar energy

C. possibly because the ice caps in the poles are melting

D. only due to the effect of the inertia of the earth' s climate

69. On the basis of their models, scientists believe the opinion that__________.

A. the climate of the world should be becoming cooler

B. the new Ice Age will be delayed by the greenhouse effect

C. the man-made warming effect helps to increase the solar effects

D. it will take thousands of years for the inertia of the earth's climate to take effect

70. If the assumption about the delay of a new Ice age is correct, ____________.

A. ice would soon cover the northern hemisphere

B. the greenhouse effect could work in favor of the earth

C. the best way to overcome the cooling effect would be to burn more fuels

D. the increased levels of carbon dioxide in the atmosphere could warm up the earth even more quickly

感染性休克的最常见病因是（）

A.革兰阴性菌

B.革兰阳性菌

C.病毒

D.螺旋体

E.真菌

甲建设单位与乙施工单位于2008年5月10日签订一份施工合同，2008年5月20日，乙施工单位发现甲建设单位隐瞒了施工现场周边真实地质条件，如果按合同施工，将增加近30%的施工费用，遂与甲建设单位协商但遭到拒绝。

下列关于行使撤销权要求的表述中，不准确的是( )。

A．债权人行使撤销权的必要费用，由债务人负担

B．撤销权的行使范围以债权人的债权为限

C．债务人以明显不合理的低价转让财产，给债权人造成损害的

D．债务人放弃其到期债权，给债权人造成损害的

旅游团对计划中预定当天的风味餐提出退餐，并自行安排到他处用餐。地陪最佳的做法是（）。

A.劝其按约定的时间前往餐厅

B.告知风味餐厅不允许退餐

C.若旅游团执意退餐，则告知其要赔偿餐厅损失

D.陪同旅游团到他处用餐

已知水泥必须消耗量是41200t，损耗率是3%，那么水泥的净用量是（）t

A.39964

B.42436

C.40000

D.43474