Passage One
Many people believe thatbeavers are intelligent animals. After all，their dams are fine examples of engineering. The engineering featsof beavers are well known, but it will be useful to recall their main features.
A pair of beavers willconstruct a dam across a river. The water held back by the dam overflows thebank on either side of the river, flooding the adjacent ground and forming apond. At some point in the pond the beavers then build their home, which iscalled a lodge. This consists of a conical pile of branches and sticks of twoto six feet in length held together with mud and stones, the top of whichprojects above the waterline. It serves as a shelter from the elements, arefuge from enemies and a base for food supplies to be drawn upon in winter.
From an engineering point ofview the lodge could hardly be improved. Not only does it contain a centralchamber just above water level,but it also has one or more escape tunnels,well-insulated walls and a vertical chimney, which regulates the temperatureinside and gives air-conditioning. It is altogether a cunning piece of construction,with all modern conveniences. It is，in fact,better protected against the effects of flooding than manyhuman habitations.
Trees are essential tobeavers. They eat the bark on the upper branches,and in order to reach thesethey must fell the trees. Tree-felling is a skilled job, as anyone who hasfelled even a sapling knows. But beavers fell more than saplings. A pair issaid to be able to fell a tree four inches in diameter in 15 minutes. They doit by gnawing all round the trunk,as high up from the ground as they can reach.They often build platforms of mud and earth to enable them to cut through thetree where the trunk is narrower.
The engineering skill ofbeavers is to a large extent a result of their ability to use their front pawsas hands. A female will carry her young held under her chin with her front pawswalking on her hind legs. A similar method is used by all beavers whentransporting stones or mud,although they also carry such materials on theirbroad flat tails. The forepaws are also used for burrowing and for draggingheavier logs.
It is easy, therefore, to seewhy people should talk about the beaver’s skill, cleverness and intelligence.However,the structure of the beaver’s brain gives no indication that the animalis any more intelligent than other rodents. Any of its actions,which appear tobe the result of a higher order of reasoning,can be shown to be due to instinctand are suspected of being the outcome of an inborn pattern of behavior.
Beavers fell trees mainly to____.()
A、build dams
B、build their lodges
C、gain food
D、exercise their jaws
【正确答案】：C
【题目解析】：细节理解题。从第4段第二句可知其目的主要是为了获取食物。答案为C。