如何学好情态动词
(Modal verbs)
can: 从客观角度陈述人们都了解的客观事实
●can 表示客观能力, 与先天、后天能力无关。
Birds can fly up into the sky easily.
鸟儿可以轻易地飞到天上去。
Luke can speak Chinese very fluently.
鲁克的汉语说得很流利。
●can表示人人都了解的客观可能性或听话人已知的客观事实。
If you are brave enough, all difficulties can be overcome.
如果你不畏艰险，所有的困难都一定会克服。
Correct ideas can be transformed into a material force that changes the world.
正确的理念一定能够转化为改变世界的物质力量。
I hear that you are going to Thailand. It can be dangerous to be there, I think.
听说你要去泰国，我看到那儿去挺危险的。
may: 表示说听双方均不确切，相当于I am not sure
●推测或了解可能性
The man you are looking for may be in that room.
May I have a talk with you?
He may never succeed without your help.
●基于may自身的不确定性，常置于句首，用来表示祝愿
May success attend you! 祝你成功!
(May) God bless you! 愿上帝保佑你!
●You can/may come at any time. (口语中can和may从不同含义角度均可使用。)
ought to: 从客观角度表示安排、责任或义务
●You ought to do the cleaning after school BECause you are on duty.
你放学后应该做卫生，因为今天你值日。
You ought not to write so carelessly.
(It is the students responsibility.学生应该做好的事)
Everybody should /ought to help each other in the study, shouldnt / oughtnt they?
(在反义疑问句中should和ought to有时可以前后交叉使用，起到主客观互补的作用)