-----How many students are there in the classroom? ---- .They are all on the playgr

问题补充：

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

------- .They are all on the playground.

A. No one

B. None

C. Nobody

D. Everyone

答案：

A. No one

(答案→)B. None

C. Nobody

D. Everyone

解析：本题的含义为在教室里有多少学生，回答语说他们都在操场上，所以没有一个在班级，表示数量上一个都没有可用none来回答，故本题选B。