乘人之危的民事行为是可以变更和撤销的民事行为。（）

在Visual FoxPro中，组合框的Style属性值为2，则该下拉框的形式为
A) 下拉组合框
B) 下拉列表框
C) 下拉文本框
D) 错误设置

读亿级和万级的数时，只要按照个级的读法来读就可以了。[ ]

小儿时期白细胞总数的特点是()

A．婴儿期约10×10⁹/L

B．6岁以后接近成人水平

C．8岁以后接近成人水平

D．初生时(15～20)×10⁹/L

E．婴儿期可因哭闹、进食、疼痛等影响发生波动。

阅读理解。

      Modern man has cleared the forests for farmland and for wood, and has also carelessly burned them. More than that, though, he has also interfered (干涉) with the invisible bonds between the living things in

}the forests. There are many examples of this kind of destruction. The harmfulness of man's interference

can be seen in what happened many years ago in the forest of the Kaibab plateau (凯亚巴布高原) of

northern Arizona. Man tried to improve on the natural web of forest life and destroyed it instead.

      The Kaibab had a storybook forest of large sized pine, Douglas fir, white fir, blue and Engelmann

spruce. In 1882 a visitor noted, "We, who ... have wandered through its forests and parks, have come

to regard it as the most enchanting region it has ever been our privilege (特权) to visit."This was also the

living place of the Rocky Mountain mule deer. Indians hunted there every autumn to gather meat and skins. The forest also had mountain lions, timber wolves and bobcats that kept the deer from multiplying too

rapidly.

    Then, in 1906, President Theodore Roosevelt made the Kaibab a national game preserve. Deer hunting was forbidden. Government hunters started killing off the deer's enemies. In 25years' time, 6,250 mountain lions, wolves and bobcats were killed. Before the program, there were about 4,000 deer in the Kaibab, by 1924, there were about 100,000.

     The deer ate every leaf and twig they could reach. But there was not nearly enough food. Hunting of

deer was permitted again. This caused a slight decrease in the deer herd (鹿群),but a far greater loss

resulted from starvation (饥饿) and disease. Some 60 percent of the deer herd died in two winters. By

1930 the herd had dropped to 20,000 animals. By 1942 it was down to 8,000.

1. The destruction of the environment of the Kaibab resulted from           .

A. turning the forest into cultivated land

B. interfering with natural cycle of forest life

C. forest fires caused by man's carelessness

D. cutting the trees for building materials

2."Engelmann spruce"(Para. 2) is most likely the name of        .

A.a tree    

B.an animal    

C.a mountain    

D.a game

3. The number of the deer in the Kaibab had increased enormously in       years' time.

A.25      

B.6          

C.18          

D.12

4. Years later, large numbers of deer in the Kaibab died mainly because of          .

A.the cold            

B.the organized kill

C.the shortage of food  

D.the poor management

“过程研究”的主要成果是模式（）、控制论模式、社会系统模式。