All he did was （to help）the homeless children为什么要填 to do 课本上有一句和这个很相似 all i have ever wanted to do was (travel） 这不就是原型么.

All he did was （to help）the homeless children为什么要填 to do 课本上有一句和这个很相似 all i have ever wanted to do was (travel） 这不就是原型么.
All he did was （to help）the homeless children
为什么要填 to do
课本上有一句和这个很相似 all i have ever wanted to do was (travel） 这不就是原型么.

All he did was （to help）the homeless children为什么要填 to do 课本上有一句和这个很相似 all i have ever wanted to do was (travel） 这不就是原型么.
动词不定式做表语,不过这里的to 也可以省略的

不定式作表语

这不是不定式作目的状语吗？怎么是表语呢？！！！！！！！！！！！！