After three minutes,the teacher asks some students to act out their dialogue.( In pairs,one is the farmer,the other one is a customer.)

Step 4 Writing 

Pre-writing

　　This exercise lets students collect and list information,then select what they think is most important and organize it for presentation.

Task 1:The students gather information that they need and plan what they want to write.

While-writing

Task 2:The students write a poster to encourage more people to buy their green food.

1.The students select and organize what they want to write and write a poster.

2.The students check their mistakes in their poster.

3.The students rewrite their poster.

An example of how to present a poster

Buy the best fruits here.

We only sell green food in this shop!

Best choice at best price!

Safe,healthy,clean,fresh.Far away from any pollution.

No chemical fertilizer,all organic fertilizers

Clean air,clean water

No poison,no pesticides

Home in heaven

Healthy food means healthy life.

Far away from diseases,without worries,full of happiness.( one reason ) After-writing

　　The students show their poster in class.

Writing tips

　　In writing a poster,make sure it has:

　　☆An attractive title;

　　☆Explain the reasons that you sell green food;

☆Explain why your green food is of good value;