前有do后无to的用法。

具体参考如下：
（1）连词连接两不定式前面的有do后面的to do的to省略，如：
I have nothing to do but watch TV all day long. 短语：have nothing to dobut do….
Tom have no choice but to give it up. 短语：have no choice but to do
在nothing but句型中,有do无to是指nothing 前有do的任何形式出现,but后的动词前就不能出现to,如:
He did nothing but piddle away the time.他不做事，只是混日子。

He could do nothing but stand and wonder.他只得惊奇地站着不动。

Jimdoes nothing but play basketball in the morning.
Now I want nothing but to go off to the Western Hills.
This man lives for nothing but to gather money.这个人的一生除了聚财以外别无目地。

Jim chose nothing but to buy a basketball that morning.
（2）用is连接，不定式作表语时前面主语有do时后面表语to do的to省略，如：
What I want to do is stay at home.
What I want to do next Sunday is see mygrandparents .
The only thing that he can do is wait.
What I want is to stay with you.
（3）注意这里说的前有do后无to的前面的do要是实意动词do,不能是助动词do
自测题：
1. He did nothing but ____.
sleep
2. He said nothing but ____there.
stand
3. I have no choice but ____ up this badbehavior.
give。