help to do sth./ help sb.do sth.二者的意思都是"帮忙做么事"
但是一个是直接加不定式,另外一个是接宾语.做题目的时候就要好好看清楚了.
can't help doing sth.这个是个固定搭配 意思是"情不自禁做..."
例如:She is so beautiful that i can't help missing her day and night.
而且还有:can’t help to do sth = 不能帮助做某事
例如:He knows nothing about it,so he can’t help to do any of your work.
根据以上分析,常见的就这4种用法吧.