From my research, the question had the following choices:
the number of songs played on each channel
the weather conditions of the city
the number of music lovers in the city
the duration of each concert
Among the choices, the correct answer is "the number of music lovers in the city". The more concerts there are in a city corresponds to the number of music lovers. Radio channels usually play music, so having a lot radio channels in a city must mean that there is a large audience.
