Final answer:
Option 4, which states that all the listed options are limitations of radio as an advertising medium, is correct. The limitations involve station-switching during ads, high commercial clutter, and retaining listener attention. The advertising model for radio is indirect and faces competition from subscription services like SiriusXM.
Step-by-step explanation:
The question concerns the limitations associated with the use of radio as an advertising medium. Limitation 4 states that 'All of these are limitations of radio as an advertising medium,' encompassing limitations 1 to 3. These limitations include the tendency of listeners to change stations during commercials, the high clutter of commercials per hour on radio, and the difficulty in retaining listener attention to radio commercials.
The radio industry must navigate unique challenges as it's impossible to charge listeners directly for conventional broadcasts. Instead, stations sell advertising to collect revenue. However, the effectiveness of radio as an advertising medium is less in comparison to social media and internet, especially for certain demographics. Moreover, with services such as SiriusXM offering subscriptions for commercial-free listening, conventional radio faces increased pressure as consumers may opt for these excludable services.