if 从句该用什么时态

if 从句该用什么时态 请看看下面这道: 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。