1. Because it rained all day, we stayed home. -> Because of the rain, we stayed home.

2. We delayed our trip because of the bad weather. -> Because the weather was bad, we delayed our trip.

3. The water in most rivers is unsafe to drink because it's polluted. -> Because of pollution, the water in most rivers is unsafe to drink.

4. You can't enter this area because of not having an official permit. -> Because you don't have an official permit, you can't enter this area.

5. Mark didn't go to work yesterday because he didn't feel well. -> Because of feeling unwell, Mark didn't go to work yesterday.

6. Edward failed the course because he missed the final exam. -> Because of missing the final exam, Edward failed the course.

7. You'll be fatter because of eating too much sugar. -> Because you eat too much sugar, you'll be fatter.

8. You got bad marks because you were lazy. -> Because you were lazy, you got bad marks.

9. Because he isn't careful, she always makes mistakes in his paper. -> Because of his carelessness, she always makes mistakes in her paper.

10. Because of too much smoke, we have to wear masks. -> We have to wear masks because of the excessive smoke.

11. Many people began wearing jeans because they were cheap. -> Many people began wearing jeans because they were inexpensive.

12. Since he was careless, Tom lost the game. -> Tom lost the game because he was careless.

13. Because of the cold weather, the crops are late this year. -> The crops are late this year because of the cold weather.

14. Mary was worried because Tom was late. -> Mary was worried because of Tom's lateness.

15. Tom walked slowly because his leg was bad. -> Tom walked slowly because of his bad leg.

16. I came here because I want the English course. -> I came here because I want to take the English course.

17. Because of the dust in the room, I can't go in. -> I can't go into the room because of the dust.

VI. Use "Because" or "because of":

1. It was difficult to deliver the letter because the sender had written the wrong address on the envelope.
2. Rescue attempts were temporarily halted because of the bad weather.
3. Just because I don't complain, people think I'm satisfied.
4. They visited their friends often because they enjoyed their company.
5. Paul may not go to the football game because of his grades.

V. Combine each pair of sentences, using "Because", "Since" or "As":

1. The teacher is sick. We'll have no class tomorrow. -> Because the teacher is sick, we'll have no class tomorrow.

2. She walked slowly. Her leg was injured. -> She walked slowly since her leg was injured.

3. Mary looks happy. She has just got good marks. -> Mary looks happy because she has just got good marks.

4. It got dark. I couldn't read the letter. -> As it got dark, I couldn't read the letter.

5. He came to the office 10 minutes late. He missed the first bus. -> Since he came to the office 10 minutes late, he misse