—I think it's both useful and _______.

—Really?

　       1   you can't eat up your whole lunch, do you throw it away?  Most kids do. But Mr. Zhang won't let you! Mr. Zhang is a teacher at a senior middle school. The 60-year-old man saw a student    2    a half piece of cake into the trash can. He was   3   angry that he   4    and ate it.

        “I just didn't want    5    food, ” he said. “I had little to eat when I was young. ”

If you have 6 been hungry, you can never understand how precious（宝贵的） food is. You might have enough food 7 . But many people didn't. Do you know that there are about 300 million hungry kids in the world? Every five seconds, a child dies 8 hunger somewhere in the world.

         What can you do? The first step is changing your attitude. Respect all the work what goes into making food. Farmers work hard to plant crops. Your parents spend a lot of money    9  food for your family. When you throw away your lunch, you are throwing away their hard work.

         So, if you can't finish    10    a big piece of cake, wrap it up and take it home. Or remember to buy a small one next time.

① Paper can be r      . We'd better not throw it away.

② It is important to try to save e      .

③If we don't protect our e      , the earth will be destroyed.

④ Our teacher tells us to collect r       plastic bags.

⑤ Gold, silver and iron are all m      .

从方框中选择最佳选项完成对话，有两项多余

a. The smoke created by the factories goes into the air every day.

b. The air here is much more polluted than that in my country.

c. We needn't worry about the problem.

d. I don't believe that any single country can do anything about it.

e. The environment problem is more serious than before.

f. What methods do you use to solve it?

g. Let's protect our home together.

A: I think the biggest environment problem in my country is air pollution.

B: Yes, I agree.      Of course, my country has much less industry.

A: There are so many factories and cars.       And the number of cars is bigger than before.

B: The problem is now on a truly global scale.       

A: I think you're right. Our earth is in danger now.       If we don't protect it together, the future will be hopeless. It needs all the countries in the world to deal with this problem.

B: Yes.       If everyone does some things for the environment, I hope we can have a better life.