The final two sentences of the passage suggest that answer C is the best choice. "Composers such as Alexander Glazunov, Sergei Prokofiev and Igor Stravinsky studied under Rimsky-Korsakov. Additionally, the mid-twentieth century composer Dmitri Shostakovich studied under Glazunov, creating a legacy of musical understanding that persisted well beyond the era of The Five." While the author does not explicitly state that Rimsky-Korsakov was the most influential, he is the only composer who is specifically linked to later composers. these noted composers include Rimsky-Korsakov's own students (Glazunov, Prokofiev, and Stravinsky) and one of his student's students (Shostakovich). Based on this, it is reasonable to conclude that the author would agree that Rimsky-Korsakov was the the most influential of "The Five." While the other individuals listed int he answer choices had a definite influence on music and composed notable works, none of them is specifically linked to later composers in the passage.