By the time he was ten,Edisonexperiments in chemistry.A. had already done　　　　B. already ha

发布时间：2020-08-15 02:10:10

By the time he was ten,Edison    experiments in chemistry.
A. had already done　　　　
B. already had done
C. was already doing　　　　
D. already did

网友回答

A. had already done　　　　
B. already had done
C. was already doing　　　　
D. already did
解析：by+过去时间，谓语用过去完成时态。
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