if引导的宾语从句有什么用法呢？

Question

如题所述

Answer 1

if的用法如下：

1、表示条件：如果。主句用将来时，if从句用现在时表示将来。

He will come if you invite him.

2、是否：whether连接宾语从句。

I wonder if he is ill.

3、表示虚拟：假如，要是。时态：可以表示过去，现在和将来的情况，它的基本特点是时态退后。

A、同现在事实相反的假设。

一般过去时should(would)+动词原形：If they were here,they would help you.

B、表示于过去事实相反的假设。

过去完成时should(would)have+过去分词：If she had worked harder,she would have succeeded.

C、表示对将来的假想。

一般过去时should+动词原形：If you succeeded,everything should be all right.

were+不定式would+动词原形：If you should succeed,everything would be all right.

should+动词原形：If you were to succeed,everything should be all right.