Which of the following is not a unit for measuring alternating frequencies?

Volts is the correct choice because it is a unit used to measure electrical potential or voltage, rather than frequency. In the context of measuring alternating frequencies, the other options are all related to the measurement of how often a wave cycles in a second, which is what frequency represents.

Cycles per second, Hertz, and kilocycles all refer directly to frequency: cycles per second is a traditional unit that describes the number of complete cycles a waveform goes through in one second, Hertz is the modern standard unit that specifies the same concept (with 1 Hz equal to 1 cycle per second), and kilocycles, while somewhat dated, represents 1,000 cycles per second. Therefore, these terms are units that quantify frequency, distinguishing them from volts, which is solely a measure of electric potential.