题目内容：
When a teacher hopes students to do exercise of a sentence pattern--Is it+adj．(colour)?He／She would say，“I think of a colour ball，do you want to know its colour?”The students would ask：“Is it white／yellow／black／green?”and so on．This way possesses some characteristics of communicative activities，which are superior to sentence exercises of audio-lingual method，this is because__________．
A．there is information-gap between dialogues B．the responder has freedom of choice
C．the questioner gets other’s feedback
D．the responder knows what the questioner saying
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