A、Because the destination is very far. B、Because they can keep warm. C、Because the trip is very dangerous. D、Because the trip is

Animals do many different, amazing things to get through the winter. Some of them travel to other places where the weather is warmer or they can find food. Many birds travel in the fall. (32) Because the trip can be dangerous, some travel in large flocks. For example, geese fly in noisy, "V"-shaped groups. Other kinds of birds fly alone. (33) How do they know when it is time to leave for the winter? Scientists are still studying this. Many see transference as part of a yearly cycle of changes that a bird goes through. The cycle is controlled by changes in the amount of daylight and the weather. Most birds transfer shorter distances. But how do they find their way to the same place each year? (34) Birds seem to navigate like sailors once did, using the sun, moon and stars for direction. They also seem to have a compass in their brain for using the Earth’s magnetic field. Other animals transfer, too. (35) There are a few mammals, like some bats, and whales that travel in search of food each winter. Many fish transfer. They may swim south, or move into deeper, warmer water. Insects also transfer. Some butterflies and moths fly very long distances. For example, Monarch butterflies spend the summer in Canada and the Northern U. S. They transfer as far south as Merico for the winter. Most insects go much shorter distances. Many, like white ants and Japanese beetles, move downward into the soil. Earthworms also move down, some as far as six feet below the surface.