should，would，could，must，might，may，can的区别：
1、can (could)表示能力，could主要指过去时间。表惊异、怀疑、不相信等态度。主要用于否定句、疑问句或感叹句中。
2、may (might)表允许，might可以指过去时间，也可指现在时间，语气更委婉。在回答以may引起的问句时，多避免用这个词，而用其它方式，如Yes, please. / Certainly.表可能（事实上）。可以指过去时间，也可以指现在时间，但语气更加不肯定。
3、must表示义务。意为“必须”（主观意志）。表示揣测。意为“想必、准是、一定”等，只用于肯定句。
4、 shall表征询意见，用于第一、第三人称疑问句。表说话人的意愿，有“命令、允诺、警告、决心”等意思，用于第二、第三人称陈述句。
5、will表意愿，用于各种人称陈述句。表请求，用于疑问句。表示某种倾向或习惯性动作。
6、should表义务。意为“应该”（某件事宜于做），用于各种人称。表推测，意为“想必一定、照说应该、估计”等。
7、would表意愿，表委婉地提出请求、建议或看法。表过去反复发生的动作或过去的一种倾向。
拓展资料
should
1、I should exercise more
我应该多锻炼一些。
2、All visitors should register with the British Embassy
所有游客都必须到英国大使馆登记。
3、I should have gone this morning but I was feeling a bit ill
今天早晨我本应该走的，但是我觉得有点不舒服。
4、You should have no problem with reading this language
阅读这种语言你应该没问题。
5、Should I or shouldn't I go to university?
我该不该去上大学呢？
would
1、No one believed he would actually kill himself
没有人相信他真的会自杀。
2、The statement added that although there were a number of differing views, these would be discussed by both sides
这项声明还称，虽然双方观点存在若干分歧，但将就这些分歧展开讨论。
3、Ordinarily it would be fun to be taken to fabulous restaurants
一般来说，跟别人去豪华餐馆吃饭会是件乐事。
4、They said they would give the police their full cooperation
他们说他们愿意与警方通力合作。
5、She asked me what I would like to do and mentioned a particular job
她问我想干什么，然后提到了一份工作。
could
1、For my return journey, I felt I could afford the extra and travel first class
至于回程，我觉得我能多花点钱坐头等舱。
2、Though he had a temper and could be nasty, it never lasted
虽然他爱发脾气，而且有时还很讨厌，但向来都只是一阵儿。
3、He could have made a fortune as a lawyer
他本可以当律师挣大钱的。
4、Doctors told him the disease could have been caused by years of working in smokey clubs
医生们告诉他这种疾病可能是由于多年在烟雾缭绕的俱乐部工作所致。
5、Their hope was that a new and better East Germany could be born
他们希望能够诞生一个崭新的、更加美好的东德。