B:	because they go from hardback to paperback
b iː WORD_BOUNDARY b ɪ k ʌ z WORD_BOUNDARY ð eɪ WORD_BOUNDARY ɡ oʊ WORD_BOUNDARY f ɹ ʌ m WORD_BOUNDARY h ɑ ɹ d b æ k WORD_BOUNDARY t ə WORD_BOUNDARY p eɪ p ə ɹ b æ k WORD_BOUNDARY