A listener can tune a car radio to one AM radio station out of several AM radio stations simultaneously broadcasting on the AM radio band. The process allowing multiple AM radio stations to coexist within a single band is called:

A.  time-division multiplexing
B.  amplitude-division multiplexing
C.  frequency-division multiplexing
D.  quadrature multiplexing

Multiplexing describes the process of combining multiple signals into one. The two most common forms are:

Time-division multiplexing - During this technique, multiple signals are broken up into frames and assigned to their own time slots. Also noteworthy is that each signal takes up the entire bandwidth when transmitting. This technique is mainly used for digital signals.

Frequency-division multiplexing - During this technique, the entire bandwidth available is broken up into respective frequency bands. Each of these specific bands is assigned a separate signal. Both radio and television broadcasting use this technique to transmit data.

Therefore, the process that allows AM radio stations to simultaneously broadcast on the AM radio band describes choice C, frequency-division multiplexing.