一道英语选择题（说清楚原因）
问题描述：
一道英语选择题（说清楚原因）
Mr White is of great help.You _______let him go.
A.had not better
B.had better don't
C.had better not
D.had no better
答
C
had better do sth 最好做某事
had better not do sth 最好别做某事