not
had better not do sth 最好不要做某事为什么不可以用do notdo不是助动词吗？you 'd better = you had better +动词原形，其否定形式是You had better not +动词原形（ 相当于情态动词。固定用法）do 也是动词原形啊怎么说？如果这里用do 作什么成分？这道题的答案一定是not区别：Don't speak at the meeting .