As is a subordinating conjunction. It indicates the reason. So is a coordinating conjunction. It indicates the effect.
1. As he was busy, he could not attend the party.
2. As she was not there, I left a message with her mother.
3. As it was very hot, I couldn’t do any work.
4. As he was angry, I said nothing.
5. As we have plenty of time, let’s have something to eat.
6. As tomorrow is a holiday, he will be at home.
7. As I have studied well, I am confident of passing the test.
8. As he was ill, he decided to consult a doctor.
9. As it is raining, we can’t go out now.
10. As he was not ready we went without him.
Answers
1. He was busy, so he could not attend the party.
2. She was not there, so I left a message with her mother.
3. It was very hot, so I couldn’t do any work.
4. He was angry, so I said nothing.
5. We have plenty of time, so let’s have something to eat.
6. Tomorrow is a holiday, so he will be at home.
7. I have studied well, so I am confident of passing the test.
8. He was ill, so he decided to consult a doctor.
9. It is raining, so we can’t go out now.
10. He was not ready, so we went without him.
