题目

Some mammals migrate（迁徒）. One of these is the caribou（驯鹿）. They travel to the tundra（苔原）every summer to eat the rich grasses that grow there. When the weather becomes cooler, they migrate to the warmer forests and spend the winter there. Another mammal that migrates is the humpback whale. They spend the winter in Hawaii, and the summer in the Arctic（北极的）waters. They travel to the Arctic to eat millions of small shrimp（虾）. Anther habit that some animals have to survive the cold winter is called hibernation. Animals that hibernate, rest or sleep during theIt is ____ bus. It is _____ English bus.A. a; aB. an; an C. a; an D. an; a