1.虽然我们年纪小，我们仍然能为保护环境做一些事情。
    _______ we are young, we can still _______ _______ to protect the environment.  
2.怀特一家在扔垃圾之前总是要将它们分类。
   The Whites always sort the waste before _______ _______ ______.
3.在你买新东西之前，想一想是否真的有必要。
   Think whether it is really necessary before you buy _______ _______ .
4.为了节约资源，我们要爱护我们的物品以便它们能长时间使用。
   In order to save resources, we should look after our things _______ _______ they can last a long time.
5.用陶瓷杯比用纸杯好，因为它可以重复使用。
   _______ _______ to use a china cup than a paper cup because it can be used again.

1. —_______you answer this question in
   —Sorry, I_______.  _______I answer it in English?
   —No, you_______. You _______answer it in Chinese.
2. —_______ I ask a question?
    —Yes, you _______But you_______wait a minute.
3. —_______ I use your eraser, Bill?
   —Sorry, I don't have one. Ask Mary. She_______have one.
4. —_______you help me do the shopping?
   —OK, sure.
5. —_______you sweep the floor, please?
   —OK, but I_______finish my homework first..

用may成can的适当形式完成对话。
David :Where are you going to spend your vacation this year ,Mary?
Mary :l __1__ go to Australia with my family. I'm not sure. My mother wants to go there ,but my father would like to Africa. They    2    make up their mind.
David :Will you travel by plane or by ship?
Mary :We__3    travel by ship.
David :Is it cheaper or more expensive ?
Mary : It _  4    be cheaper ,but it takes a long time.
David : l'm sure you'll enjoy yourselves.
Mary: Don't be so sure. We__5     not go anywhere.