请教下面与Unless有关的句子.
我对Unless的用法比较困惑,想请教下面的句子,然后请帮我回答以及分析一下为什么,
Which of these sentences can be rewritten with unless?
1.I will be surprised if he doesn't have an accident soon.
2.It will be better if we don't tell her anything.
3 You can have the car tonight if Harriet doesn't need it.
4 I will tell you if I can't come.
5 I am going to dig the garden this afternoon if it doesn't rain.
6 She'd look nicer if she didn't wear so much make-up.