.They out because the light’s on. Let’s go upstairs and have a look.A. mustn’t goB. can’t

问题补充：

.

They out because the light’s on. Let’s go upstairs and have a look.

A. mustn’t go

B. can’t have gone

C. couldn’t go

D. might have gone

答案：

A. mustn’t go

(答案→)B. can’t have gone

C. couldn’t go

D. might have gone

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