关于复合固定桥的叙述中，错误的是（）
A.含有四个或四个以上的牙单位
B.含有两个以上基牙
C.由两种或三种基本类型的固定桥组合而成
D.基牙数目多且分散，不易获得共同就位道
E.以上都不是复合固定桥
参考答案：E
解析：固定桥的类型有：①双端固定桥；②半固定桥；③单端固定桥和④复合固定桥。其中，复合固定桥是由①～③中的2种或3种基本类型的固定桥组合而成。故选E。
Pop music is the name for various popular，commercial music．It originated in the USA and spread through the whole world during the 1950s and 60s．It is widely liked by the young people．The best known early form of pop music was “rock’n’ roll”; another was “blues”. A more recent development is “folk rock”．Pop music has taken the place of native music in many parts of the world．It has caused the number of people for “jazz” music to become much smaller than in the 1950s and earlier, and it has now began to rule music stage productions．It is a big industry． Much pop music is without artistic value, but the work of some pop singers e.g. the Beatles, Bob Dylan, the group like Pink Floyd and Crosby, Still and Nash, is on a higher musical level. And there is still great interest in it today. Pop music concerts and festivals are held all over the world. 小题1: In this passage the underlined word "originated" means _______.
 sit is today.
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