Question

【题目】By the time he was twelve, Edison __________ to make a living by himself.

A. would begin B. has begun

C. had begun D. was begun

Answer 1

【答案】C

【解析】by the time意为“到……时”，引导的从句谓语用一般过去时时，主句用过去完成时表示已完成的动作。