Dear native English speakers.
The following are five sentence trying to express the same meaning.
1. He has been acquitted, and no wonder.
2. He has been acquitted, and it is no wonder.
3. He has been acquitted,which is no wonder.
4. He has been acquitted, and that no wonder.
5. He has been acquitted, and no wonder at that.
Question:
Which is grammatically correct?
Do they have the same meaning?