题目内容
阅读下面短文，掌握其大意，然后从各题所给的四个选项（A、B、C和D）中，选出最佳选项．
With their shiny, grey bodies, dolphins（海豚）appear to be large fish．____1____, they are really warm-blooded mammals. Although they can stay under the water for up to 15 minutes ____2____, the dolphins must come up to breathe air through a hole on top of their heads.
Dolphins are social animals. Many of them even ____3____ around humans. In addition to being playful; they are helpful to men. For example ____4____ 400 B.C. the Great poet Arion was saved from ___5____ by a dolphin. From then until now, dolphins have been helping swimmers, ____6__ in trouble. Swimmers, however ,are not ___7____ humans they help. In some parts of the world, they help men ____8____ fish.
Dolphins are very clever. Its brain is even larger than a human's. Therefore, some people think a dolphin ____9__ smarter than a man, but ____10___, brain size is not the only measure of cleverness. Besides, measuring dolphin's cleverness in other ways is not possible ___11____ men cannot talk with them. But we can almost ____12____ that dolphins can talk with each other. They make different ____13____ which seem to be at least a form of language. Up to now men ____14___ able to find out how dolphins are talking. So no one really knows what they are thinking. If we could talk with them, perhaps they could teach us to be ___15____ they seem to be.
