Imagine when you are sailing an ocean for the first time, you see a big fish swimming near your ship. You might be scared, and worried about whether it will turn over your ship for a meal. In fact, it is not a fish at all, but a gentle giant whale.
Whales are not fishes but mammals (哺乳动物). Their body temperature stays the same, and does not change with the temperature of their environment. They breathe air, so they have to come out of the water to get oxygen. Thus, they cannot afford to fall into a sleeping state for too long, since they need to be awake in order to breathe. It is thought that only half of their brains sleep at a time, so that whales are never completely asleep. Females give birth to the young. They have hair. Although they are not covered in hair or fur like many mammals, whales have some bristles (胡子), usually on their heads.
Whales are highly social animals with complex languages and intelligence. They communicate with each other using romantic sounds, called “whale songs”. Being so large and powerful, these sounds are also loud.
Whales are endangered as a result of whaling (捕鲸) from the eleventh century to the twentieth. It has attracted the attention of environmentalists and some measures (措施) have been taken to protect whales.
49. How many aspects show that whales are mammals?
A. One. B. Two. C. Three. D. Four.
50. We can infer from the second paragraph that ____.
A. whales can breathe in the water
B. if a whale sleeps too long, it will get drowned
C. in order to breathe, whales never sleep
D. whales give birth to the young on the land
51. How do whales communicate with each other?
A. By body language. B. By speaking languages.
C. By making song-like sounds. D. By giving off a smell.
52. Which of the following is TRUE according to the passage?
A. Whales are cold-blooded mammals like fishes.
B. Whales are hunted for food by people.
C. Whales are very harmful to human beings.
D. Whales are in danger because of being killed by people.