The passage cites which of the following as a factor helping to explain San Francisco's preeminence as a center for jazz music on the West Coast early in the twentieth century? A. The number of job opportunities for musicians in San Francisco's nightclub district B. The efforts by the government to enforce Prohibition in San Francisco C. The existence of venues for many different types of jazz in the San Francisco area D. The relative accessibility of San Francisco, as compared to Los Angeles, for musicians from elsewhere in the country E. The fact that San Francisco at that time had a larger African American population than Los Angeles