Postby mmmason8967 » September 21st, 2012 10:05 pm
Yes, it's repetitive. I imagine it's from a textbook and what they're doing is labouring the point a bit. The answer makes it clear that the question is about the ownership of the book, the first phrase shows that an answer can be word-for-word the same as the question apart from the ka, and the second phrase shows an alternative shorter answer.
Postby natsukoy9313 » September 22nd, 2012 7:13 am
マイケルsan is right.
Still, the latter part "B-san desu" is kind of uncessary. Even if the answer was only the latter part (without the first correct one),
that's not very correct. It should be "B-san no desu". So, just ignore the latter part.