单选题
A dolphin(海豚)looks more like a fish than certain fishes do. It is an excellent swimmer. The dolphin seems to flash through the water. Like fish, dolphins are completely at home in the water. There they play, feed, sleep, and give birth to their young. Dolphins live in the sea and can live only in the sea. Yet they are not fish. A dolphin must come to the surface to breathe. Fish can take oxygen from the water. Dolphins cannot. Like us, they breathe with lung and must take their oxygen from the air. And they are mammals(哺乳动物). Most mammals are land animals. Dolphins are evolved(进化)from land animals. Long ago, dolphin ancestors(祖先)left the land for the sea. Among the animals was a kind that would become the dolphin we know. No one is sure exactly what kind of animal it was. But there is reason to think it was related to grass-eating animals like the cow. Modern dolphins are fish-eaters.Yet their stomachs are like those of animals that eat plants. The make-up of their blood is also like that of grass-eating animals.
单选题
The best title for this passage is ______. A. Dolphins B. Fish C. Mammals D. Cows
单选题
What can we learn from the first paragraph? A. A dolphin is a special kind of fish. B. Dolphins can't swim very quickly. C. Dolphins can live only in the sea. D. Dolphins produce their babies on land.
【正确答案】
C
【答案解析】[解析] 本题是事实细节题。由文章第一段最后一句话“Dolphins live in the sea and can live only in the sea．”可知海豚仅能生活在海洋里，所以选项c正确。再由第一段第一句、第二句和第五句可知选项A、B、D均不符合文意。
单选题
Different from fish, dolphins ______. A. live on land. B. breathe with lungs. C. breathe under water. D. live without oxygen.
单选题
Dolphins are evolved from ______. A. fish-eating mammals. B. sea animals. C. grass-eating fish. D. land animals.
【正确答案】
D
【答案解析】[解析] 本题是事实细节题。由文章第三段第二句话“Dolphins are evolved from land animals.”可知本题答案为D。
单选题
What can be inferred from the passage? A. Dolphins have highly evolved. B. Mammals don't eat plants at all. C. All fishes developed from land animals. D. Dolphins were once closely related to humans.