A)
1. Im not British.
2. They aren't Brazilian.
3. It's not in South America.
4. You aren't French.
b)
1. Am I in room 10 ? Yes, I'm
2. Is it Italian ? No, it isn't
3. Are they students ? No they aren't
4. Is he from the USA ? Yes, he is.
5. Are you sure ? No, I'm not.