40. —Shall Tom go and play football? —Not he has finished his homework.A. whenB. ifC. unl

问题补充：

40. —Shall Tom go and play football?

—Not he has finished his homework.

A. when

B. if

C. unless

D. once

答案：

A. when

B. if

(答案→)C. unless

D. once

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