The answer is B.
Radio is a far wider-reaching tool of media then newspaper will ever be. Not only is it a more engaging tool, but it is an easier tool to access. Anyone can listen to the radio, as long as they have a car or even an internet connection. You don't need to have the hassle of newspaper subscriptions and all of that. You would have a far bigger audience if you did an hourly commercial on the radio. Which, of course, is what you want.