根据短文意思填写单词．

　　A science book gives facts．Some science books tell about animals．Some tell about plants．Some tell about outer space．This page tells about 　　1　　．

　　Do you know that some animals live in the 　　2　　?The whale is not a fish．It cannot breathe in the water．It swims in the water．But it comes up for air．

　　The 　　3　　 whale(鲸)is the world's biggest animal．There are other sea animals, too．One is called the dolphin(海豚)．Dolphins need air to live．They breathe(呼吸)air, as whales do．Dolphins are very clever．They seem to be able to speak to each other．

　　Many other animals live near the sea．Seals(海豹)and otters(水獭)like the sea．They swim and play there．They eat fish and sea 　　4　　．Seals and otters have thick fur(皮毛)．The fur keeps them 　　5　　．