单选题
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.
单选题
From the passage we can learn that ______.
【正确答案】
D
【答案解析】[解析] 本题考查推理判断。根据常识可知，A项不正确；根据第一段第二句“Birds do travel vast distances，but mammals also migrate.”可知，B项错误；根据第一段第六、七句“Another migrating mammal is the Alaska fur seal. These seals breed only in the Pribilot Islands in the Bering Sea.”可知，C项错误。故这三项均可排除。所以，答案是D。
单选题
The phrase "An example" underlined in Paragraph 1 refers to an example of a ______.
【正确答案】
A
【答案解析】[解析] 本题考查细节理解。根据文章第二、三句“Birds do travel vast distances，but mammals also migrate. An example is the caribou...”可知，上文提到哺乳动物也迁徙，紧接着就说其中一个例子是……。所以，这个例子应指迁徙的哺乳动物。因此，答案是A。
单选题
All the mammars ale mentioned as migrating ones EXCEPT ______.
【正确答案】
B
【答案解析】[解析] 本题考查细节理解。根据文章第三句和第六句“An example is the caribou，reindeer that graze on the grassy slopes of northern Canada. Another migrating mammal is the Alaska fur seal.”可知，caribou，reindeer和Alaska fur seal都被以哺乳动物提及。所以，只有B项没有提及。因此，答案是B。
单选题
Where can you See from the air the migration of the mammals?
【正确答案】
D
【答案解析】[解析] 本题考查细节理解。根据文章第三、五句“An example is the caribou，reindeer that graze on the grassy slopes of northern Canada... Their tracks are so well-worn that they are clearly visible from the air.”可知，驯鹿在加拿大北部的草原吃草，他们的迁徙路径可以清晰地从空中看到。因此，答案为D。
单选题
Which of the following is NOT true?
【正确答案】
B
【答案解析】[解析] 本题考查是非判断。根据文章最后一句“In winter，the whales move to warm waters to breed and give birth to their young.”可知，在冬天，Alaska fur seals迁徙到温水中去繁殖和生养后代。故B项说法不正确。所以，答案是B。
单选题
Together ______ of Alaska fur seals swim down the Pacific Coast of North Americ
【正确答案】
【答案解析】[解析] 本题考查细节理解。根据文章中的“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.”可知，母海豹和幼海豹会从白令海到北美太平洋海岸；而公海豹也会从白令海南下，只不过他们没有母海豹和幼海豹走的远罢了。所以，答案是C。
单选题
Which of the following is NOT described in the passage?
【正确答案】
B
【答案解析】[解析] 本题考查是非判断。根据文章最后一句“In winter，the whales move to warm waters to breed and give birth to their young.”第七句“These seals breed only in the Pribilot Islands in the Bering Sea.”第三句“An example is the caribou, reindeer that graze on the grassy slopes of northern Canada.”可知，A、C、D三句在文中都有提及。只有B项在文中没有提到。所以，答案是B。
单选题
Whales live on ______.
【正确答案】
A
【答案解析】[解析] 本题考查细节理解。根据文章倒数第二、三句“Whales eat huge quantities of plankton(浮游生物)．These are most abundant in cold polar waters.”可知，鲸以大量浮游生物为生。所以，答案是A。
单选题
How many kinds of migrating mammals are mentioned in the passage?