4.You must not plant trees in very dry earth . Trees must not be planted by you in very dry earth.
3. Sixteen-year-olds should be allowed to drive. (先改为否定句，再改一般疑问句)
People may catch fish in the river.
Fish may be caught in the riven cook delicious meals. Delicious meals can be cooked by my mother.
I don’t think the work should be done at once.
序号 原形 过去式
主要含义
1
can
2 may
could 1.能力2.请求/准许3.可能性 might 1.请求/准许2.可能性 *3.祝愿
3 must
must 1.义务(必须); 2.猜测(肯定)
had to
4 need needed
需要
5 dare
dared
敢
6
will
would
愿意
7 shall should 1.征求意见 2“应该”(should) 3
The exam can be passed (by you) if you study hard.
Can the exam be passed (by you) if you study hard?
water(浇水)
They must water trees every day. Trees must be watered by them every day. Must trees be watered by them every day?
3.Parents should allow teenagers to drive the car.
Teenagers should be allowed by parents to drive the car .
Should teenagers be allowed by parents to drive the car ? 4.You can pass the exam if you study hard.
Sixteen-year-olds shouldn’t be allowed to drive.
Should sixteen-year-olds be allowed to drive?
Yes they should./ No, they shouldn’t.
4. I think the work should be done at once. (改为否定句)
关于情态动词及情 态动词的被动语态
情态动词有哪些?
1. can /may/must/ will / shall / should / ought to
2. need /dare 3. had better/ would rather, used to /
have to / be able to
2
情态动词的含义
情态动词的含义
序号 原形
过去式
主要用法
8
be able to was/were able to
“能够”（能力）
9 have to
had to
“不得不/必须”
10 ought to
ought to
“应该”
11 used to
“ 过去（常常）”
12 had better
13 would rather
“最好” “ 宁愿”
4
含情态动词的被动语态： 情态动词+be +PP
can/could be done must be done should be done may/might be done had better be done have to be done
否定式：情态动词+not + be + p.p
can/could not be done must not be done should not be done may/might not be done had better not be done have not to be done
2. Students will use these textbooks next term. These textbooks will be used next term by students .
3. You should water trees often . Trees should be watered by you often .
1.I can finish the work. The work can be finished by me. Can the work be finished by you?
2.We should plant many more trees. Many more trees should be planted by us. Should many more trees be planted by us?
疑问式：情态动词+ 主语+ be + p.p
can/could +主语 +be done must +主语 + be done should +主语 + be done may/might +主语 + be done had +主语 + better be done have +主语 + to be done