你好，请问下面例句中做表语的不定式为何前面没to?
After four days in a hospital, John was fired. And all he had done was go outside and get the license number.
你的句子也可以加上to，写成：
After fourdays in a hospital, John was fired. And all he had done was to go outside andget the license number.
在英语中，当all sb do作主语时，其后用作表语的不定式可以省略 to，也可以不省略 to。又如：
All I do is type letters. 我的工作是打印信件。
All he does is complain. 他只能发牢骚。
All she does is talk about herboyfriend. 她就不停地讲她的男友。
All he did was open the door. 他所做的只不过把门打开。
All I did was press this button.我所做的只不过按这个电钮。
All I did was touch the window, and itbroke. 我只是碰了一下窗户，玻璃就碎了。
All I had done was give him a littlepush. 我所做的不过是轻轻地推了他一下。
