III. 

1. although

2. come

3.were

4. sun

5. how much

6. unpolluted

7. which

8. being talked 

9. have been

10. shall we

III.

1. Although the traffic was bad, we arrived on time.

2. I'll show you around the city when you come.

3. If energy were inexpensive and unlimited, many things in the world would be different.

4. Solar energy can be cheap and clean.

5. I am writing this to tell you that how much you are missed and loved.

6. We should learn about keeping the enviroment unpolluted.

7. The pencil which I write is made in Japan.

8. We don't want to be talked like that.

9. They have been in Hanoi since last Sunday.

10. Let's go shopping, shall we?

IV.

1. This coffee is too hot to drink. 

2. He drives so carelessly that he is sure to have an accident.

3. His parents were disappointed that he failed the final examinations.

4. Do you know what the depth of this river is?

5. He is a very skillful carpenter.

6. There are many celebrations in our country of a year (cũng có thể điền celebrities, cả hai từ trong trường hợp này đều dùng được cả nhé!)

7. We celebrate our Independent Day on September 2nd.

8. You must be carefull when you open that door.

9. We can save our natural resouces by using solar energy.

10. We can't clean up our polluted rivers and seas over night.