The development of the American
art form known as abstract
expressionism in the 1950s

Answer;

Abstract Expressionism, broad movement in American painting that began in the late 1940s and became a dominant trend in Western painting during the 1950s. ... The most prominent American Abstract Expressionist painters were Jackson Pollock, Willem de Kooning, Franz Kline, and Mark Rothko.

in the 1950s, country music came into its own before rock-n-roll took off in the 60s while jazz and classical music continued to innovate

the answer is b. hope this