Directions: For each blank in the following passage, there are four choices marked A, B, C and D. Choose the one that is most suitable and mark your answer by blackening the corresponding letter on the answer sheet.

In fact, there was hardly any activity or social event that could not be set to Music. Weddings, births, christening, funerals, picnics, parades-- 21 had their musical accompaniment.

After the American Civil War (1860-1865), the Negroes had gained their freedom and were ready 22 a new type of music, 23 that would preserve their musical traditions but be fast and happy 24 their 25 freedom. They wanted something they could play as professional musicians for both black and white audiences. Jazz was the answer. It combined themes from Negro work songs, spirituals and blues, set to a fast beat, 26 the musicians improvising (即兴而作) as they went along, like the funeral marching bands. To be good, a musician had not only to remember his part but also 27 able to invent new variations on the spur (激励) of the moment.

Jazz 28 the people, but popular 29 is changed many times in form, style, and tempo. Each change added something 30 .

21.

A. which

B. that

C. all

D. those