(   ) 3. We should solve the problem        to the factories.

   A. by writing   B. by wrote

   C. by write   D. by writes

(   ) 2. The air is badly. And there's more water        in the world.

   A. pollution;pollute   B. polluted;pollution

   C. pollution;pollution   D. pollute;polluted

(   ) 1. The river is full of rubbish. Everyone should        cleaning it up.

   A. play part in   B. play a part in

   C. join   D. play a part

5. Please remember to throw       (垃圾) into the bins.

4. There are many        (优点) of riding a bike.

3. How much did the car        (花费) you?

2. The        (底部) of the bottle is very thick.

1.        (木头) desks are stronger than        (塑料) ones.

14. turn...into         

 13. throw... into...