Final answer:
The relatively low cost of radio advertising time makes it an effective medium through which advertisers can build more reach and frequency into their media schedules. The correct option is B.
Step-by-step explanation:
The relatively low cost of radio advertising time makes it an effective medium through which advertisers can build more reach and frequency into their media schedules. Reach refers to the number of individuals or households that are exposed to a particular advertisement, while frequency refers to the number of times those individuals or households are exposed to the advertisement within a given period. Radio advertising allows advertisers to reach a wide audience and increase the frequency of exposure, helping them to effectively promote their products or services.