Question

1. He was sick so he couldn't go to work.

2. He was sick, so he couldn't go to work.

3. He was sick so that he couldn't go to work.

(What is the difference among them? Does #1 mean #2 or #3? What is the meaning of #1?)
Ms. Sue
Number 1 is correct; a comma is not needed. He was sick so he couldn't go to work.

Number 3 -- omit "that."