英语：情态动词、反意疑问句?（选择题）

英语：情态动词、反意疑问句?（选择题）①This is a green jeep,＿?A.is it B.isn't it C.is this D.isn't this②Tom's never late for class,＿?A.is he B.isn't he C.has he D.hasn't he ③Nothing is difficult if you put your heart into it,＿?A.is it B.isn't it C.are they D.don't you④You'd better not smoke,＿?A.did you B.didn't you C.had you D.hadn't you请帮忙想一下.谢谢.请说明为什么。谢谢。