1、不定式分句作主语补语时通常带to,但在某些句型中也可省略to.例如：
All I did was empty the bottle.
All you do is talk about cars.
What I really wanted to do was drive all night.
The only thing I can do now is go on by myself.
上述诸例中的不定式分句之所以能省略to,有一个条件,即主语部分必须具有一个主动词do,这个do可以是限定动词形式,也可以是非限定动词形式,而且不论什么时体形式均可.
2、it has to do是省略了引导词that的定语从句.关系代词that代替先行词all,在从句中作do的宾语,所以可以省略.have to do是英语习语,意为“与XX有关”.