阅读理解

　　Whales(鲸)are the biggest animals in the sea．They are much bigger than any animal on land．The largest whales are more than 30 metres long．

　　Whales live in water, but they are not fish．They have warm blood(血)and they breathe(呼吸)air through(通过)a hole in the top of their head．They can stay under water for about an hour without breathing．

　　There are two kinds of whales．One kind has a big mouth with teeth．Its mouth is four metres deep．It can eat other large animals of the sea．This kind is called a killer(杀手)whale．

　　The other kind of whale is much larger than the killer whale．It has no teeth．It has rows of bone(骨)in its mouth．Small sea life is caught in these bones．These whales also have a very small throat(喉)．They cannot eat anything larger than an apple．

　　Whales have skin(皮肤)but not scales(鱼鳞)．Their skin is gray or black in colour．Under their skin is a lot of fat(脂肪)．This fat is used to make oil(油)．The oil is used for many things such as making soap．

　　Some whales have oil in their heads．This is pure(纯的)oil and is very expensive．From 114 to 228 litres(升)of oil can be found in the head of some whales．Sometimes on big whale has hundreds of litres of oil．