Sure! Here are the combined sentences for both exercises:

**Exercise 2:**
1. Jason was very tired, so he went to sleep early because he was very tired.
2. You can't speak to John at the moment, so you can’t speak to him because he is busy.
3. Tomorrow is a public holiday, so all the shops will be shut since it is a public holiday.
4. Simon was busy, so he couldn't come to the meeting because he was busy.

**Exercise 3:**
1. I am sick, so I do not go out because I am sick.
2. The water is polluted, so we can’t swim in that river because the water is polluted.
3. She walked slowly because her leg was injured.
4. Mary looks happy because she has just got good marks.
5. Nga has had a sore leg, so she had difficulty in walking because she had a sore leg.
6. I didn’t come soon because there was a traffic jam.