If you really want yourself to be in good health,you must____always____so much.

题目

If you really want yourself to be in good health,you must____always____so much.
A.not be smoking
B.not have smoked
C.not to smoke
D.be not smoking
我选的是D,
详细说说……小弟感激不尽……

答案

这道题你的问题在于情态动词的用法没掌握好.
情态动词有can (could),may (might),must,have to,shall (should,will (would),dare (dared),need (needed),ought to等.
它们的用法就是：肯定：情态动词 + be
否定：情态动词 + not be
此题只是使用了情态动词的否定用法和动词ing表状态延续的用法.