if从句的时态
问题描述：
if从句的时态
答
if有两个意思：“是否”和“如果”.当做“是否”讲时一般引导宾语从句,时态依据时间状语来做决定,如：I don't know if he will come tomorrow.当做“如果”讲的时候,又分为两种情形：1.真实性条件状语从句,此时遵循“主将从现”原则,即主句用将来时,而if条件状语从句用一般现在时来代替将来时.如：If it doesn't rain tomorrow,I will go shopping with my friends.2.虚拟性条件状语从句,初中阶段常接触对现在和对将来的虚拟,此时主句多用过去将来时（would+动词原形）,而从句用一般过去时（V-ed）.如：If I knew his telephone number,I would tell you.
若果你是初中学生,掌握这些就足够了,如果你是高中生,请继续追问,会附上虚拟性状语从句的详细用法.