by the time 的句子中，用完成时，还是进行时？谢谢。

Question

And isn't it amazing that by the time children are two or three years old they are stringing sentences together?
这里为什么用are stringing 呢？是不是因为句子的意思，而不仅仅是依据by the time

Answer 1

by the time
到…的时候
句中时态应该用完成时。

And isn't it amazing that by the time children are two or three years old they are stringing sentences together?孩子两三岁的时候,他们就能把句子串在一起，是不是很令人吃惊?
本句中的by the time表达的意思是“在...的时候”，相当于at the time, 是因为句子的意思，才用的现在进行时。所以，你的理解是对的。
by the time如果翻译成“到...时候为止”，就应该使用完成时了。

Answer 2

分情况，看主句还是从句
by the time 有两个意思:
一:by the time可以翻译为:这时候,在此时.相当于at the/that time.

By the time he had lost contact with the Party.

这时他已和党失去联系。
By the time we had settled in the third bus.

这时我们已在第3辆大汽车里坐好。
二:by the time,意为:在....之前已经....

by the time our teacher came in ,we had started speaking English.

在老师进来前,我们都已经开始讲英语了.
by the time when got to the bus station,the bus had left.

在我们到达车站时,汽车早就开走了

补充：by the time 引导时间状语从句,相当灵活
by the time 引导时间状语从句, 有些和when相似, 就像这句:
By the time you come back, the meal will be ready. 典型的主将从现.
By the time he is ten, he has outgrown his older brother.
他十岁的时候就已经长得比他哥哥高了.
(从句用一般现在时, 主句用现在完成时, 说明现象).
By the time we arrived, the meeting was over. 均为过去时态.
By the time we arrived, the train was already moving. 前面过去时, 后面过进.
By the time you receive this letter, I will have left this city for my hometown.本回答被提问者采纳