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情态动词本义（can could should）知识点总结
之前咱们聊过了情态动词和have done在一起的用法，今天咱们来看看情态动词的本义。
如果从考察覆盖面最广的角度上来看，情态动词在考试中主要出现以下的考法：
can / could 强调客观能力 / 表示许可 / 推测
will / would 体现主观意愿 / 表将来
may / might 语气最弱，强调不确定的情况或较弱的可能性 / 表示许可
must 语气最强，态度非常坚决、情况非常确定、语气非常绝对
should提出建议 / 描述正常状态下的行为 / 描述在现有条件下将来即将发生的事情
shall / ought to 强调义务和责任，或命令与预期，语气较强
need 提出需求，强调必要性
但是就像我们昨天说过的，情态动词一定在描述句中某个比较特殊的情感态度语气。所以如果我们光探讨这些既彼此独立又互相有交集的功能定义，掌握效果肯定会打折扣。咱们还是一起看看在过去的题目中这些东西的用法，有个环境会更有体会一些。
在题目里考察理解最多的，应该是can / could和should。
can / could强调客观能力 / 表示许可 / 推测
should
提出建议 / 描述正常状态下的行为 / 描述在现有条件下将来即将发生的事情
The soccer team has been doing well this season, so they should win the championship.
在现有条件下将来会发生的事。他们应该能赢得冠军。这句话能不能用could？could要不就是过去，要不就表示语气偏弱，哪个和这句都不吻合。
- It's eight o'clock already. Jack should be here by now.
- Oh, he told me that he was going to see his dentist and wouldn't be back until ten.
正常状态下的行为。他应该到了。
- Will my son be all right soon, doctor?
- Well, he should be, if he takes these tablets.
在现有条件下将来会发生的事。他应该会康复。
It is a rule in our school that no books can be taken out unless you have a library card.
表示许可。书不能被带出去。
How can I help them to understand when they won't listen to me?
表示能力。我怎么才能帮助他们（潜台词：我没能力帮助他们）。
- What should I wear to the party?
- Well, it isn't very formal. You can wear whatever you like.
表示许可。你可以穿任何你想穿的衣服。
- You must be looking forward to your trip back to Sydney.
- Yes. I can't wait any longer.
表示能力。我都不能等了。
- Has your brother found a job?
- Not yet. There are many jobs that he can do but he seems unwilling to do anything.
表示能力。有好多他能做的事。
While a great CV can get you in the door, a great interview gets you the job.
表示能力。简历能带给你面试机会。
- These grapes look really beautiful.
- They should! See the price, $3.99 a pound! Too expensive, aren't they?
正常状态下的情况。这么贵的葡萄就应该好。
- Could you please have my car ready today?
- Sure, the damage is not that serious, so it should be ready by 5:00 pm.
在现有条件下将来会发生的事。5点车应该能修好。
- Make a turn at the corner.
- Should I make a right or a left? I'm terrible at directions.
描述建议。我是应该往左还是往右？
