问题：

[单选,材料题]

根据下列材料，回答下面的题目
    Rhythm and blues，or R&B，is a 26 0f music that came out of the jazz，blues and gospel music that was bein9 27 by African Americans 28 the l930s and l940s．Over the years，  the term has commonly been used to describe 29 popular music this community was played at the time．This more upbeat,exciting type of music caught on 30 a big way，and for the first time，African Americans 31 their own style of commercial music．
    In the late l930s，many big bands broke up 32 smaller units and formed“jump blues”bands 33 played loud music with a strong dance beat，quickly 34 popular in the dance halls at the time． Earlv R&B 35 were those of Count Basie，Louis Jordan and Lionel Hampton．Basie had a hit in l937 with One 0’clock Jump． 36 Jordan had a string of hits from the late l930s through the l940s．By the mid l940s，R．M．Blues by Roy Milton and The Honeydripper by Joe Liggin each 37 0ne million copies． ‘
    The new music style 38 to evolve and was gaining 39 rapidly．In Annapolis，more than 50，000 people 40 up to a concert with seating for 8，000．There was a traffic 4l for seven hours．
    Rhythm and blues has come a long way 42 American African musicians of the mid 20th  century developed their own style of 43 music based on some more conservative styrles at the time.R&B had huge success in the l950s and l960s before making an even 44 comeback as contemporaryR&B 45 the l980s on．

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