How many students are there in the classroom?- All of them are practicing the new

问题补充：

--- How many students are there in the classroom?

--- ．All of them are practicing the new song in the music hall．

A. Nobody; singing

B. None; singing

C. Twenty; to sing

D. No one; to sing

答案：

A. Nobody; singing

(答案→)B. None; singing

C. Twenty; to sing

D. No one; to sing

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