Reading Comprehension
Directions: Read the following passage. Choose the best answer from the four choices marked A, B, C and D for each question. 

     Many people believe that beavers are intelligent animals. After all, their dams are fine examples of engineering. The engineering feats of beavers are well known, but it will be useful to recall their main features.
     A pair of beavers will construct a dam across a river. The water held back by the dam overflows the bank on either side of the river, flooding the adjacent ground and forming a pond. At some point in the pond the beavers then build their home, which is called a lodge. This consists of a conical pile of branches and sticks of two to six feet in length held together with mud and stones, the top of which projects above the waterline. It serves as a shelter from the elements, a refuge from enemies and a base for food supplies to be drawn upon in winter.
     From an engineering point of view the lodge could hardly be improved．Not only does it contain a central chamber just above water level，but it also has one or more escape tunnels，well-insulated walls and a vertical chimney，which regulates the temperature inside 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 many human habitations.
     Trees are essential to beavers．They eat the bark on the upper branches，and in order to reach these they must fell the trees．Tree-felling is a skilled job，as anyone who has felled even a sapling knows． But beavers fell more than saplings．A pair is said to be able to fell a tree four inches in diameter in 15 minutes．They do it 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 the tree where the trunk is narrower.
     The engineering skill of beavers is to a large extent a result of their ability to use their front paws as hands．A female will carry her young held under her chin with her front paws walking on her hind legs．A similar method is used by all beavers when transporting stones or mud，although they also carry such materials on their broad flat tails．The forepaws are also used for burrowing and for dragging heavier logs.
     It is easy，therefore，to see why people should talk about the beaver’ s skill，cleverness and intelligence．However，the structure of the beaver’s brain gives no indication that the animal is any more intelligent than other rodents．Any of its actions，which appear to be the result of a higher order of reasoning，can be shown to be due to instinct and are suspected of being the outcome of an inborn pattern of behavior.