question: What are the four common styles of mandolins ?
answer: the Neapolitan or round-backed mandolin , the carved-top mandolin and the flat-backed mandolin .
turker_answer: The four common styles of mandolins are , the Neapolitan or round-backed mandolin , the carved-top mandolin and the flat-backed mandolin .
rule-based: The four common styles of mandolins are the Neapolitan or round-backed mandolin , the carved-top mandolin and the flat-backed mandolin .