Explanation: A Class B amplifier is defined by its operating characteristic where the output device (transistor or vacuum tube) conducts for exactly one-half of the input signal's cycle. This corresponds to 180 degrees of the input waveform. This mode of operation allows Class B amplifiers to achieve greater efficiency than Class A amplifiers, which conduct for the full 360 degrees. However, because a single Class B amplifier only processes half the signal, two such amplifiers are typically used in a "push-pull" configuration to reproduce the entire input waveform accurately, with each device handling one 180-degree half-cycle. Options A (360 degrees) describes a Class A amplifier. Option B (greater than 180 degrees and less than 360 degrees) describes a Class AB amplifier. Option C (less than 180 degrees) describes a Class C amplifier.