can, may, must, should区别
1. Can (过去式could) 可表示下列三种意思：
A. possibility (可能性) （表示理性的猜测，与事实村子与否无关。）
1) 专家也可能犯错。
Even experts can make mistakes.
2) 她的表现是我们所能期望的最佳状态了。
Her performance was the best that couldbe hoped for.
B. Ability (能力)
3) 你能解决这个问题吗？
Canyou solve this problem?
4) 约翰十岁就会说五种语言。
John couldspeak five languages by the age of ten.
5) 下星期我就能解决这个问题
I will be ableto solve this problem next week. (√)
I will cansolve this problem next week. ( ×)
6) 事情总会水落石出的。
The truth will be found out. (√ )
The truth can befound out. (× )
C. permission (允许)
7）我可以用你的电话吗？
Can I use your phone?
8）二十年前妇女在选举时不能投票。
A couple of decades ago, women couldnot vote in elections.
2. May (过去式might) 可表示下列两种意思：
A. possibility (可能性) （表示推测可能存在的事实）
9）我们可能永远到不了山顶。
We maynever reach the top of the mountain.
10）可能有一些怨言。
There mightbe some complaints.
B. permission (允许)
11) 如果没什么可说的，你可以走了。
You maygo now if you have nothing else to say.
12）请问你用不用计算机？
Might I ask whether you are using your computer?
3. Must （过去式用had to)
A. Logical necessity (推测的必然性)
13）一定是哪里出错了。
There mustbe some mistakes.
14）他一定很有钱。
He must have a lot of money.
15) 一定得弄出那么大的声音吗？
Needthey make so much noise? (√)
Dothey need to/haveto make so much noise? (√)
Mustyou make so much noise? (×)
16）他们一定得弄出那么大的声音。
They will have tomake a lot of noise. (√)
They will mustmake so much noise. (×)
B. Obligation or compulsion (义务或强制)
17）晚上十点一定要回来。
You must be back by ten p.m.
18）晚上十点一定要回来吗？
Needshe be back by ten p.m.? (√)
Doesshe need to/have tobe back by ten p.m.? (√)
Mustshe be back by ten p.m.? (×)
4. should /ought to
A. tentative inference (试探性的推论)
19）我们从这应该可以看得到。
We should/ ought tobe able to see it from here.
20）这个时候她应该到家了。
She should/ought tobe home at this moment.
B. obligation (义务)
21）你应该照他的话做。
You should/ought tofollow what he says.
22）开会之前你应该准备周全。
You shouldget ready before attending the meeting.
an, may, must, should区别
1. Can (过去式could) 可表示下列三种意思：
A. possibility (可能性) （表示理性的猜测，与事实村子与否无关。）
1) 专家也可能犯错。
Even experts can make mistakes.
2) 她的表现是我们所能期望的最佳状态了。
Her performance was the best that couldbe hoped for.
B. Ability (能力)
3) 你能解决这个问题吗？
Canyou solve this problem?
4) 约翰十岁就会说五种语言。
John couldspeak five languages by the age of ten.
5) 下星期我就能解决这个问题
I will be ableto solve this problem next week. (√)
I will cansolve this problem next week. ( ×)
6) 事情总会水落石出的。
The truth will be found out. (√ )
The truth can befound out. (× )
C. permission (允许)
7）我可以用你的电话吗？
Can I use your phone?
8）二十年前妇女在选举时不能投票。
A couple of decades ago, women couldnot vote in elections.
2. May (过去式might) 可表示下列两种意思：
A. possibility (可能性) （表示推测可能存在的事实）
9）我们可能永远到不了山顶。
We maynever reach the top of the mountain.
10）可能有一些怨言。
There mightbe some complaints.
B. permission (允许)
11) 如果没什么可说的，你可以走了。
You maygo now if you have nothing else to say.
12）请问你用不用计算机？
Might I ask whether you are using your computer?
3. Must （过去式用had to)
A. Logical necessity (推测的必然性)
13）一定是哪里出错了。
There mustbe some mistakes.
14）他一定很有钱。
He must have a lot of money.
15) 一定得弄出那么大的声音吗？
Needthey make so much noise? (√)
Dothey need to/haveto make so much noise? (√)
Mustyou make so much noise? (×)
16）他们一定得弄出那么大的声音。
They will have tomake a lot of noise. (√)
They will mustmake so much noise. (×)
B. Obligation or compulsion (义务或强制)
17）晚上十点一定要回来。
You must be back by ten p.m.
18）晚上十点一定要回来吗？
Needshe be back by ten p.m.? (√)
Doesshe need to/have tobe back by ten p.m.? (√)
Mustshe be back by ten p.m.? (×)
4. should /ought to
A. tentative inference (试探性的推论)
19）我们从这应该可以看得到。
We should/ ought tobe able to see it from here.
20）这个时候她应该到家了。
She should/ought tobe home at this moment.
B. obligation (义务)
21）你应该照他的话做。
You should/ought tofollow what he says.
22）开会之前你应该准备周全。
You shouldget ready before attending the meeting.