一般现在时表示将来时46.I don't know when he ,but when he ,

来源：学生作业帮编辑：作业帮分类：英语作业时间：2024/05/19 21:00:45

一般现在时表示将来时
46.I don't know when he ______,but when he ______,I'll let you know.
A.will come/comes B.comes/will come C.comes/comes D.will come/will come
为什么这里不能两个comes?不是comes一般现在时可以表示将来时吗?

A两句虽然都含有when引导的从句,但意义不同,用法也就不同.
前半句when he will come 是个含有when引导的时间状语从句,使用将来时,意思是我不知道他什么时候（将要来）
后半句是个含有when引导的条件从句,虽然是when,但从意思上理解是：当他回来时（他只要一回来）我就让你知道,所以是条件句,使用一个条件句的重要原则（主将从现）的原则.所以主句I'll let you know用了将来时,而从句but when he comes用了现在时.

一般现在时表示将来时46.I don't know when he ______,but when he ______, 46.I don't know when he ____a__,but when he ______,I'll let I don't know when he ____,when he ______,i will tell you Choice 1.I don’t know when he ___,but when he ___,I’ll speak I don't know when he ____,but when he ____,I will let you kn I don't know you as well as he does but,______ your friend,I 1. I don’t know when ______ the dictionary. I didn’t know why he looked angry when I patted him ______. I didn’t know why he looked angry when I patted him ______.A I don't know ______ it was that he moved to another city,but we don't know when ______ (start) I don't know when he ＿（come）back.