29.Which of the following is true according to the passage?

　　A.Though dolphin is a kind of fish, it can breathe air like us.

　　B.Dolphins often kill sharks for food.

　　C.Dolphins probably communicate with each other through a kind of sound.

　　D.Dolphins have formed their own groups and they help only the members in the same group.

　　答案：C

　　[解析]這是一個細(xì)節(jié)理解題，從第二段的最后一句可以得知“The sounds they make also appear to be some kind of communication.”(他們發(fā)出的聲音似乎就是一種交流的方式)，故應(yīng)選C。

　　30.What would the next paragraph probably talk about?

　　A.Why dolphins are as intelligent as human beings.

　　B.How the dolphins help and care men in modern times.

　　C.How the dolphins were killed for commercial purposes and what we should do to protect them

　　D.What more discoveries scientists have made about dolphins.