七、should 和ought to
should 和ought to 都为"应该"的意思，可用于各种人称。
——Ought he to go?
——Yes. I think he ought to
表示要求，命令时，语气由 should（应该）、had better最好）、must（必须）渐强。
八、 had better表示"最好"
had better 相当于一个助动词，它只有一种形式，它后面要跟动词原形。
had better do sth
had better not do sth
It is pretty cold. You'd better put on my coat
She'd better not play with the dog.
had better have done sth表示与事实相反的结果，意为"本来最好"。
You had better have come earlier.
九、 would rather表示"宁愿"
would rather do
would rather not do
would rather… than… 宁愿……而不愿。
还有would sooner, had rather, had sooner都表示"宁愿"、"宁可"的意思。
If I have a choice, I had sooner not continue my studies at this school.
I would rather stay here than go home. = I would stay here rather than go home.
