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根据短文内容及首字母提示，填写所缺单词，使短文意思完整。每空限填一词。

Many people say dolphins are very intelligent (聪颖的). They seem to be able to think, understand, and learn things quickly. But are they c  1．   like humans or more like cats or dogs? Scientists say dolphin intelligence is s  2．   to human intelligence in some ways. How?
Like humans, every dolphin has a “name”. I  3．    is a special whistle (哨声). Scientists think dolphins, like people. “t  4．  ” to each other about a lot of things, such as their age, their feelings, or finding food. And, like humans, dolphins use a system (系统) of sounds and body language to c   5．  . But understanding their conversations is not easy for humans. No one “speaks dolphin” yet, but some scientists are trying to learn.
Dolphins are also social animals. They live in groups, and they often come to play games from different groups and have f 6．   , just like people. In fact, playing t  7．   is something only intelligent animals do.
Dolphins and humans b  8．    make plans to get something they want. In the seas of southern Brazil, dolphins use an interesting way to get food. When fish are n   9．   a boat, dolphins signal (发信号) to the fishermen to put their nets (网) in the water. And the men can catch a lot of fish. What is the advantage for the dolphins? Why do they h  10．   the men? The dolphins can get some of the fish.