13.1 1.go for a drink 2.go inside 3.go and see it 4.do another exercise 5.have a rest 6.ask someone for help
13.2 1.don't be 2.Don't make 3.smoking 4.play 5.try 6.Read 7.Be 8.Don't let 9.turn on 10.Watch
13.3 1.Close the door，please./ Please close the door.
2.Let them not touch the vase./ Don't let them touch the vase.
3.No smoking.
4.Mum，let us ride a bicycle.
5.Let's go swimming together，shall we？
6.Let us bake a birthday cake for you，will you？
7.Be quiet.
8.Don't eat too much sweet food.
13.4 1.Please stand up./ Stand up，please.
2.Don't be late.
3.Please don't come in./ Don't come in，please.
4.Let Tom not walk on the grass./ Don't let Tom walk on the grass.
5.Let's join the basketball club together.
6.Lucy，close your eyes./ Close your eyes，Lucy.
7.Children，please do your homework carefully./ Please do your homework carefully，children.
8.Don't put your bag on the sofa，will you？
9.Please be careful./ Be careful，please.
10.Let Tom fix this bicycle.
11.No dogs in the bakery！
12.Never play with fire！