当直接引语是一般疑问句、反意疑问句或选择疑问句,变成间接引语时,由连词whether或if 引导.例如：
“Have you finished your homework?” he asked me.
→ He asked me if / whether I had finished my homework.
Susan asked him,“You have met my brother,haven’t you?”
→Susan asked him whether / if he had met her brother.
“Is the window open or closed?” he asked me.
→ He asked me whether / if the window was open or closed.
注意：当if和whether引导宾语从句时可以互换,但在动词不定式前或介词后只能用whether.例如：
I don’t know whether to accept or refuse his invitation.
I worry about whether I hurt her feelings.动词不定式是啥？我们老师没讲英语术语的意思，所以我们班的学生总是学得晕乎乎的，望解释。。。动词不定式就是to+动词原形的一种形式