1. Fill in the blanks with because, because of, since.

1. （1） She was well paid, she did her work well.
3. （2） the earth is round, why do we not fall off?
5. （3） I didn't climb the mountain raining.
7. （4） He failed again he didn't work hard.
9. （5） you don't know the answer,I will ask someone to help you.
11. （6） She is popular among classmates her kindness.