Which of the following is not a way in which the field of journalism has changed in recent years?

a. Satellite radio has challenged the effectiveness of AM and FM stations.
b. Although national newspapers have struggled, local newspapers have maintained their presence.
c. A few open-air television networks have given way to hundreds of cable channels.
d. Social media has assumed a central role in everyday life.

b. Although national newspapers have struggled, local newspapers have maintained their presence.