had better表示"最好"

　　had better 相當(dāng)于一個(gè)助動(dòng)詞，它只有一種形式，它后面要跟動(dòng)詞原形。

　　had better do sth

　　had better not do sth

　　It is pretty cold. Youd better put on my coat.

　　Shed better not play with the dog.

　　had better have done sth表示與事實(shí)相反的結(jié)果，意為本來(lái)最好.

　　You had better have come earlier.