Question 21 is based on the passage you have just heard.

听力原文

    (19) [An endangered species of whale is experiencing a small baby boom off the coast of America.] The North Atlantic right whale is one of the rarest species of whale on the planet, numbering only about 411. But the Center for Coastal Studies said Friday that its aerial survey team spotted a mum with two babies in Cape Cod Bay a day earlier. That brings the number seen in nearby waters alone this year to three. That’s big news because the whale population has been falling, and no baby whales were seen last year. In all, seven baby whales have been spotted so far this year. (20) [The whale population has become endangered due to commercial whaling activities in recent years.] This is because they are sometimes hunted for their meat or their skin. Over-hunting could lead to the disappearance of the whale population, possibly causing major problems to the global food chain. (21) [The whales give birth off the southeast coast of America in the winter and travel to feeding grounds off the northeast coast in the early spring.] The northeast coast is a critically important source of food. The animals often feed close to shore. This provides watchers on land with “unbeatable views of one of the rarest of marine mammals.” It’s illegal to get within 1,500 feet of the animals without a federal research permit, so whale watchers are discouraged from attempting to get close to the whales.

21. Why do the whales travel to the northeast coast of America in the early spring?（鲸鱼为什么在早春时节游向美国东北海岸？）

解析：B。录音中说到，鲸鱼冬天在美国东南海岸分娩，早春时游到美国东北海岸觅食。因此B项正确，To look for food对应录音中的feeding grounds，为正确答案。

错项排除：录音中没有提到鲸鱼是为了交配或躲避捕猎者而前往美国东北海岸，排除A项和C项。录音中提到，鲸鱼冬天在美国东南海岸分娩，并非东北海岸，D项错误。