高一英语语法惯用法：这个if从句要用什么时态

Question

如题所述

Answer 1

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.

Answer 2

if 如果，引导的条件状语从句，表示将来的情况时，使用一般现在时。如：
if he comes please tell me. 如果他来了请告诉我。
if it is dark i will stay at home. 如果天黑了我就呆在家里。