Ответ:
I.
HAVE you got a brother? Видишь, в вопросе стоит have? Значит и в ответе будет форма have, в данном случае have not. => b) No, I haven't.
II.
- Good morning, Jill!
- Good morning, Alice! Would you like some porridge?
- No, thank you. But I would like some juice and ham sandwich.
- Ok! Here you are. Help yourself.
- Thank you, Jill.
III.
- How are you?
- I'm fine, thanks. What about you?
- I'm fine too! Where are you from?
- I'm from Russia. And what about you?
- I'm from Great Britain.
- Have you got a pet?
- Yes, I have. I have got a dog.