一道关于动词时态的英语题.By the time he was ten,Edison already did experiments in chemistry.中,为什么用already did,而不用already had done?

一道关于动词时态的英语题.By the time he was ten,Edison already did experiments in chemistry.中,为什么用already did,而不用already had done?
一道关于动词时态的英语题.
By the time he was ten,Edison already did experiments in chemistry.
中,为什么用already did,而不用already had done?

一道关于动词时态的英语题.By the time he was ten,Edison already did experiments in chemistry.中,为什么用already did,而不用already had done?
By the time he was ten,Edison already did experiments in chemistry.
因为是过去时态.
完成时要对某一时刻有影响.这里面只是在叙述过去的事实,没有说出什么影响.

by the time
通常都会用过去完成,不过本句意在强调过去的一个动作,经历.不强调完成性
所以也可以用过去时