18.Dolphins (海豚)are one of the smartest animals in the world.Dolphins often eat fish and some other sea animals.They like to swim and look for food in groups. Dolphins have very good hearing.They use it to find things under the water.Scientists believe dolphins can even talk to each other through a special whistle(哨子聲).Just like people from different places speak different languages,there are different kinds of dolphins' whistles. Dolphins live in the sea,but they are not a kind of fish.They have babies in the way that cows(奶 牛)and cats do,and feed their babies with milk.A female (雌性)dolphin has a baby every two to three years. Dolphins are very friendly.But there are not many kinds of dolphins left.People kill them for food and other things.If people stop killing them,perhaps there will be more dolphins in the future. Information Card