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.

　　81. From the passage we can learn that ______

　　A. people migrate like animals

　　B. only birds migrate

　　C. the female fur seals migrate only to the Gulf of Alaska

　　D. not all mammals migrate

　　82. The phrase "An example" underlined in Paragraph 1 refers to an example of a ______

　　A. migratory mammal

　　B. place where animals migrate

　　C. migrating bird

　　D. person who associates migration with birds

　　83. All the mammals are mentioned as migrating ones EXCEPT ______

　　A. caribou B. fin whale

　　C. reindeer D. Alaska fur seal

　　84. Where can you see from the air the migration of the mammals?

　　A. In the Pribilot Islands. B. In the Bering Sea.

　　C. In southern California. D. In northern Canada.

　　85. Which of the following is NOT true?

　　A. Whales breed in winter.

　　B. Young whales are given birth in cold waters.

　　C. Alaska fur seals give birth to the young only in one area.

　　D. Alaska fur seals are born in warm weather.

　　86. Together ______ of Alaska fur seals swim down the Pacific Coast of North America.

　　A. mothers and the young

　　B. fathers and the young

　　C. parents and the young

　　D. seals and whales

　　87. Which of the following is NOT described in the passage?

　　A. Whales migrate to breed and give birth to their young.

　　B. Whale-watching in Boston in summer is attracting.

　　C. Seals breed in the north before migration.

　　D. Reindeer feed on grass.

　　88. Whales live on ______

　　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

　　89. How many kinds of migrating mammals are mentioned in the passage?

　　A. Four. B. Three.

　　C. Two. D. One.

　　90. What is the best title of the passage?

　　A. Three Types of Whales

　　B. Birds Migration

　　C. Mammals Also Migrate

　　D. Several Kinds of Migration