if 从句该用什么时态
请看看下面这道题:
I don’t know if he _________ or not tomorrow.
A. come B. comes C. will come D. is coming
【分析】此题容易误选B。认为 if 引导的是条件状语从句,
从句谓语要用一般现在时表示将来意义。其实,此题应选C,句中if
引导的不是条件状语从句(即if≠如果),而是宾语从句(即if,是否),
句意为我不知道明天他是否会来。请看以下类似试题:
(1) I don't know if she _________, but if she _________ I
will let you know.
A. comes, comes B. will come, will come
C. comes, will come D. will come, comes
选 D,第一个 if 引导的是宾语从句,第二个 if 引导的是
条件状语从句。
(2) When _________ he come? I don’t know, but when
he _________, I’ll tell you.
A. does, comes B. will, will come
C. does, will come D. will, comes
选 D,第一个 when 疑问副词,用于引出一个特殊疑问句;
第二个 when是从属连词,用于引导时间状语从句。
(3) When he _________ is not known yet. But when he _________, he will be warmly welcomed.
A. comes, comes B. will come, will come
C. comes, will come D. will come, comes
选 D,第一个 when 引导的是主语从句,第二个 when 引
导的是时间状语从句。