题目内容
―Look! What a mistake! Why?
―Sorry, I _________ on it.
A.don’t concentrate B.hadn’t concentrated
C.haven’t been concentrating D.wasn’t concentrating
D

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题目内容
―Look! What a mistake! Why?
―Sorry, I _________ on it.
A.don’t concentrate B.hadn’t concentrated
C.haven’t been concentrating D.wasn’t concentrating
D