单选题：根据下面资料，回答题： Music comes in many forms：most countries have a

根据下面资料，回答题：
Music comes in many forms：most countries have a style of their own．__ 21__ theturn of the century when jazz(爵士乐)was born，America had no prominent__ 22__ 0f its own．No one knows exactly when jazz was__ 23__ ，or by whom．But it began to be__ 24__ in the early l900s. Jazz is America’s contribution to__ 25__ music．In contrast to classical music，which __26__ for-mal European traditions．Jazz is spontaneous and free-form．It bubbles with energy， __27 __moods．interests, and emotions of the people．In the 1920s，jazz__ 28__ like America．And__ 29__ it does today．
The__ 30__ 0f this music are as interesting as the music __31__ ，American Negroes，or blacks，as they are called today were the Jazz__ 32__ ．They were brought to the Southern states __33__ slaves．They were sold to plantation owners and forced to work long__ 34__．When a Ne—gro died．his friends and relatives__ 35__ a procession to carry the body to the cemetery．In New Orleans，a band often accompanied the __36__ ．On the way to the cemetery the band played slow，so1enmn music suited to the occasion，__37__ 0n the way home the mood changed． Spirits lifted．Death had removed one of their__38__ ，but the living were glad to be alive．The band played__39__music．improvising(即兴表演)on both the harmony and the melody of the tunes 40 at the funeral．This music made everyone want to dance．It was an early form of Jazz．
A．Before
B．At
C．In
D．On