表语从句问题

Question

what i want to know is( )he likes the gift given by us.
为何这里填whether不填if啊？

Answer 1

此句属于主系表结构
what i want to know ——（主语）+is——（系动词）+表语从句(( )he likes the gift given by us)
而在表语从句中只能用whether不能用if

Tips：
有五种情况是只能用whether不能用if的：
1. 强调两方面的选择，特别是句中有or not时。如：

Let me know whether you can come or not.

2. 宾语从句前置时。如：

Whether this is true, I can\'t say.

3. 引导主语、表语、同位语从句时。如：

Whether the football game will be played depends on the weather. （主语从句）

The question is whether he can do it. （表语从句）

The question whether we should go with them must be decided at once. （同位语从句）

4. 在介词之后作介词的宾语时。如：

I haven\'t settled the question of whether I\'ll go back home.

5. 在不定式前与不定式一起组成词组时。如：

Whether to go or stay is still a question.

Answer 2

表语从句的注意事项有哪些

Answer 3

whether和if在宾语从句的话就可以相同啦，现在这句是表语从句

Answer 4

引导主语、表语、同位语从句时，只能用whether本回答被网友采纳