It is your own fault you are so tired . You oughtn’t to have stayed up so late .A. when B.

问题补充：

It is your own fault you are so tired . You oughtn’t to have stayed up so late .

A. when

B. how

C. where

D. why

答案：

A. when

B. how

C. where

(答案→)D. why

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