Can dolphins   talk? Maybe they can not talk with words,but they can talk with sounds. They show their feelings with sounds.Dolphins travel in a group.We call a group of fish a"school".They do not study,but they travel together.Dolphins are mammals  ,not fish,but they swim together like fish in a schoo1.Dolphins talk to the other dolphins in the schoo1.They give information to the others.They talk when they are happy,sad or afraid.They say"welcome"when a dolphin comes back to the schoo1.They talk when they play. They make some sounds above water.They make many more sounds under water.People cannot hear these sounds because they are very,very high.Scientists make tapes of the sounds and study them.Sometimes people catch dolphins for a large aquarium  .People can watch dolphins in a show.Dolphins do not like to be away from their school in an aquarium.They are sad and lonely.There are many stories about dolphins.They help people.Sometimes they save somebody' s life.Dolphins' meat is good,but people do not like to kill them.They say that dolphins bring good luck.Many people believe this. The word"school"in this passage means  _  .
a place for students to study a group of fish traveling together a special kind of animals a place for training dolphins