What is the first example of radio advertising?
A
The Du Pont sponsored history program, "Cavalcade of America," broadcast on the Columbia Broadcasting System
B
"Dr. John Romulus Brinkley's Lectures on Vigor and Vitality," a program featuring patent medicine
C
AT&T's "toll broadcasting" station, WEAF New York
D
RCA's use of sponsors on its National Broadcasting Company
A
B
C
D