阅读理解,根据短文内容,判断正误 People sometimes change homes. Animals do too! Some fish change homes. They swim from rivers to the sea. They swim back to the rivers when(当……的时候) they grow up. Many birds change homes too. They fly south in autumn to find food. In spring, they fly north. It is called "bird migration".
Some bears change homes. They move to warm places in winter and come back in spring. But some bears do not change homes. They sleep in caves(洞)all winter. In spring, they come out to find food.