Final answer:
The radio, with its ability to broadcast live entertainment and news, was a pivotal invention in spreading popular music during the 1950s and 1960s, shaping a shared national culture and popularizing genres like rock and roll. Hence, option (b) is correct.
Step-by-step explanation:
One invention that helped further the spread of popular music in the 1950s and 1960s was radio. The radio was key in creating an American national identity by providing live broadcasts that millions could listen to simultaneously. Its entertainment and news programming significantly influenced American culture by making certain music, like rock and roll, wildly popular across the nation. Beginning in the 1920s, shows like 'Amos 'n' Andy' and various music programs began shaping a shared national culture, with radio waves engulfing the airwaves.
By the 1930s, comedy programs and other forms of entertainment had gained popularity, contributing to the rise of a mass culture being shaped by mass media. Radio played a vital role in this transformation by being the main source of both entertainment and news. The emergence of rock and roll stars like Little Richard and Buddy Holly, who initially captured the hearts of teens through radio, illustrates the medium's profound impact on the spread of popular music.