-----第一阶段----第四讲情态动词1.情态动词的基本含义（1）can①A light spirit can bear a heavy fate.You can do it if you believe you can.②If winter comes, can spring be far behind?You can’t step into the same river twice.③You can’t benefit from others’losses.It can be good.You can be right.（2）may①You may lead a horse to the water, but you cannot make him drink. You may well surprise yourself at what strengths you have.②Your mind may be free no matter where you are.Misfortune might be a blessing in disguise.（3）mustIn order to succeed, you must have a long-term focus.When we want to more roses, we must plant trees.It must be Tom.（4）have toLife is like school. You have to pass one test to get on to the next test.To make a lasting marriage we have to overcome self-centeredness.You have got to like what you do.You’ve got to be in order to succeed.（5）shouldYou should try to seek every opportunity instead of just waiting quietly for its visit.Everyone should be wiser today than yesterday.（6）ought toMan ought to have something that he prefers to life.Everybody ought to do at least two things each day that he hates to do.（7）willYou can if you will.Heaven never helps the man who will not act.（8）would rather （或would sooner）In order to pursue light and heat, people would rather （或would sooner）lose their lives.We would rather（或would sooner）die on our feet than live on our knees.I would rather（或would sooner）forget what others owe me than forget what I owe others.（9）dareI dare not linger, for my long walk is not yet ended.Dare you be the first to eat oysters?（10）needHe who labors diligently need never despair.（11）had betterSleeping dogs had better be left alone.We’d better struggle for the future rather than regret for the past.（12）used toMy father used to say,“it is important to learn from your mistakes”.He used to smoke, but knowing what a bad habit it is, he stopped three years ago.2.情态动词+现在完成时的用法You can’t have been here.You can’t have married.You should have told me.You should have married.You shouldn’t have married.No matter what a person’s past may （might） have been, his future is spotless.God must have made every human being with a different intention.She can’t （或couldn’t） have succeeded by luck because she made every effort possible.Well into her 70s, she could easily have retired, but she preferred not to.Marsha did not accept the bad news, she should（或ought to） have taken this as a signal to look at other opportunities.If you doubt his ab ility, you shouldn’t （或ought not to） have hired him in the first place.Often when you look back, you feel that you needn’t have worried so much because a lot of things really didn’t matter.情态动词现在完成式主要有两个功能:表示已经发生的情况和表示虚拟语气.在这两个方面must/mustn’t,；can/can n’t；need/needn’t；may/mayn’t；minght/mightn’t；should/shouldn’t；ougtht等情态动词+完成式表示的意思是有一定区别的（1）表示已经发生的情况.1）must have+过去分词,表示对已发生情况的肯定推测,译为“（昨天）一定……”，如：my pain apparent the moment I walked into the room, for the first man I met asked sympathetically：“are you feeling all right?”[A]must be [B]had been [C]must have been [D]had to be2）can’t/couldn’t have+过去分词，表示对已发生情况的否定推测，译为“（昨天）一定没……”，如：Mary my letter； otherwise she would have replied before now.[A]couldn’t have received[B]ought to have received[C]has received [D]shouldn’t have received3）may/might have+过去分词，表示对已发生的事情做不肯定、可能性很小的推测，或事实上根本没发生，译为“也许……”。
如：at Florida power’s crystal river plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.（2）表示虚拟语气。
1）needn’t have+过去分词，表示做了不必须做的事，相当于“didn’t need to do”，译为“其实没必要……”。
如：you needn’t have come over yourself.as it turned out to be a small house party. we so formally.[A]needn’t dress up[B]did not need have dressed up[C]did not need dress up [D]needn’t have dressed up2）should have+过去分词，表示应该做某事但实际上未做，译为“本应该……”should not +have 过去分词表示本不应该做某事但实际上做了，译为“本不应该……”，如；I regret having left the work unfinished； I should have planned everything ahead carefully。
我本来应该事先认真地把每件事情规划的很好，但实际上作者还是没有规划好，以至工作没有完成。
3）ought to have + 过去分词，表示动作按理该发生了，但实际上未发生，译为“该……”，与should 的完成式含义类似。
如：the porter ought to have called the fire-brigade as soon as he saw the fire in the stock , which went up in smoke.4）could have +过去分词，表示过去本来可以做但却未做，译为“完全可以……”，这点与ought/should/have+过去分词用法相似。
如；what you said is right, but you could have phrased it more tactfully.5）may/might have+过去分词，表示过去可以做但实际未做，译为“（那样）也许会……”。
如：it might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.3.情态动词常考的句型：（1）may/might （just）as well “不防，最好”，与had better相近Since the flight was cancelled, you might as well go by train.既然航班已经取消了，你不妨乘火车吧。