He must be helping the old man to water the flowers ?A. is he B. isn’t heC. must heD. mus

问题补充：

He must be helping the old man to water the flowers, ?

A. is he

B. isn’t he

C. must he

D. mustn’t he

答案：

A. is he

(答案→)B. isn’t he

C. must he

D. mustn’t he

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