Question

By the time he was twelve, Edison（） to make a living by himself A.would begin B.has begun C.had b

Answer 1

答案是C，had begun

By the time he was twelve,Edison had begun to make a living by himself.
By the time表明截至到某一段时间为止，后面的句子须用完成时态对应。

Answer 2

C

Answer 3

选择C.had
By the time he was twelve, Edison had to make a living by himself.
在12岁之前爱迪生不得不自己谋生。

Answer 4

C