如果他从来不帮我,我为什么要帮他?
___Why ___should I help him if he never helps me?
如果她想要,她为什么不能买辆新车?
___Why ___shouldn't she get a new car if she wants one?
既然我能看电影,为什么还要读这本书?
___Why ___should I read the book when I can watch the movie?