按英语习惯，介词后通常不能直接跟that从句作宾语，但有个别特殊结构就在介词后先接it作形式宾语，再跟that从句，如look to it that, see to it that, depend upon it that, rely on it that, answer for it that等。
1. look to it that
Look to it that you do not fall.
Look to it that this doesn’t happen again.
2. see to it that
See to it that you are not late again.
Please see to it that the door is locked.
I’ll see to it that everything is ready in time.
I should have seen to it that she was told.
Can you see to it that the fax goes this afternoon?
Robert has seen to it that all the little leaks were shut off.
3. depend upon it that
You may depend on it that they will support you.
You may depend upon it that we shall never lose heart.
4. rely on it that
You may rely on it that he will come to meet you.
You can rely on it that I will keep your secret.
5. insist on it that
He insisted on it that I (should) go with him.
He insisted on it that we (should) accept these gifts.
6. answer for it that
I can’t answer for it that he is honest.
You have my word for it that the goods will arrive on time.
Can I take your word for it that the text has all been checked?
We only have his word for it that the cheque is in the post.