今天金山词霸的每日一句是All I have to do is learn English. 为何倒数第二个词不用Lea

下列句型中,be动词后的to可以省略,改接原型动词做表语.
All I have to do is (to ) take a good rest.(你所要做的是好好休息）
All I can do is (to)wait.(我所能做的就是等待）
What you should do is simply (to) apologize to him.
(你应做的事就是向他道歉）
All I did yesterday was (to) eat and sleep.(我昨天做的事就是吃和睡）这些句子前都含有do的某一形式,所以可以省略后面to do中的to.