题目
By the time he was thirteen, Thomas（）to make a living by himself.A. would beginB. had begunC. has begunD. was begun
By the time he was thirteen, Thomas（）to make a living by himself.
A. would begin
B. had begun
C. has begun
D. was begun
题目解答
答案
B. had begun
解析
本题考查过去完成时的用法。关键点在于理解时间状语By the time he was thirteen的语境意义。该结构表示“到他十三岁的时候”，强调某个动作在过去的某个时间点之前已经完成。此时主句需用过去完成时（had + 过去分词）。
选项分析
- A. would begin（过去将来时）：表示过去某一时间之后的打算或预测，不符合题意。
- B. had begun（过去完成时）：正确表达“到十三岁时已经完成开始工作的动作”。
- C. has begun（现在完成时）：强调动作与现在仍有联系，但题目时间“thirteen”是过去时间点。
- D. was begun（被动语态）：主语Thomas是动作执行者，需主动语态。
核心逻辑
By the time引导的时间状语从句用一般过去时（was），主句需用过去完成时表示动作在“过去的过去”完成。