Answer:
2) If pigs had wings, they would fly.
3) If he worked hard, his marks would be good.
Explanation:
Second conditional is a structure that expresses an impossible (or highly unlikely) situation. In other words, it expresses a condition that can't be met.
The structure of the second conditional is as follows:
- main clause (the condition) contains "if" and verb in past tense
- the other clause contains would+verb construction.
So, these are rewritten sentences:
2) If pigs had wings, they would fly.
3) If he worked hard, his marks would be good.
If we write the "if" clause first, we need to separate it with a comma, otherwise we don't.