话题 stop to do

话题 idea to do

话题 idea of doing

话题 do something where

话题 have sb do

话题 have sb doing

话题 spend sth doing

话题 want to do

话题 ask to do

话题 than do sb

话题 see to do

话题 aim to do

话题 feel like doing

问题 worth doing（值得做）可用于哪些句式

worth后接动词要用动名词，请问worth doing 有哪些句式可用？

问题 what we can to do sth是什么结构

We should do what we can to help the homeless people.what we can to do 是什么结构、什么成分呢？