why not doing sth还是why not do sth还是why not to do sth
问题描述：
why not doing sth还是why not do sth还是why not to do sth
答
Why not do sth
例如：Why not go to cinema?为什么不去电影院呢?
Why don't you do sth
例如：Why don't you turn to teacher for help?为什么你不找老师帮忙呢?