Some people associate migration mainly with birds. Birds do travel vast distances, but mammals also migrate. An example is the c

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问题     Some people associate migration mainly with birds. Birds do travel vast distances, but mammals also migrate. An example is the caribou, reindeer that graze on the grassy slopes of northern Canada. When the weather turns cold, they travel south until spring. Their tracks are so well-worn that they are clearly visible from the air. Another migrating mammal is the Alaska fur seal. These seals breed only in the Pribilot Islands in the Bering Sea. The young are born in June and by September are strong enough to go with their mothers on a journey of over 3,000 miles. Together they swim down the Pacific Coast of North America. The females and young travel as far as southern California. The males do not journey so far. They swim only to the Gulf of Alaska. In the spring, males and females all return to the islands, and there the cycle begins again. Whales are among the greatest migrators of all. The humpback and blue whales migrate thousands of miles each year from the polar seas to the tropics. Whales eat huge quantities of plankton. These are most abundant in cold polar waters. In winter, the whales move to warm waters to breed and give birth to their young.
Whales live on ______

选项 A、tiny plants and animals in the sea
B、the grassy slopes of northern Canada
C、their young in cold winter
D、the abundant seafood in tropic waters

答案A

解析 见文章倒数第三、四句:Whales eat huge quantities of plankton(浮游生物)。 These are most abundant in cold polar waters,所以选项A为答案。也可用排除法:选项B指的是reindeer的习性,选项C文中未提及鲸以幼仔为生,选项 D指的是tropic water,与 polar water相反:所以只有选项A正确。
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