1. C

2. B

3. C

4. A

5. B

1. I was watching da nang fireworks on tv, and at that time the power went out (WHILE)

=> The power went out whild I was watching Da Nang fireworks on TV.

2. It is raining so we won't have pratice today (SINCE)

=> We won't have practice today since it is raining.

3. The sun rises in the morning after a rooster crows very early (BEFORE)

=> A rooster crows very eraly before the sun rises in the morning.

4. I failed the quiz in math; there fore, I have to stay for tutoring. (BECAUSE)

=> I have to stay for tutoring because I failed the quiz in math.

5. You need to study a lot of new words to do well on the quiz (SO THAT)

=> You need to study a lot of new words so that to do well on the quiz.

 Doing/ reduce/ of/ exercise/ obesity/ physical/ helps/ risk/ the.

doing physical exercise helps reduce the risk of obesity.

3. Social/ teenager’s/ to/ important/ networks/ life/ are/ a.

social networks are important to teenager's life.

4. Reading/ most/ the/ activities/ among/ teenagers/ these/ and/ crafts/ making/ books/ are/ popular.

reading books and making crafts are the most popular activites among these teenagers.