Explanation: In a bias circuit, a resistor's primary function is to create a specific voltage drop to set the operating point for a transistor or tube. If you measure the same voltage to ground on both sides of a 100K-ohm resistor, it signifies that there is no voltage drop across it. By Ohm's Law (V=IR), zero voltage drop implies zero current flow through the resistor (assuming it's not shorted). This condition would disrupt the intended bias and prevent the associated active device from functioning correctly, indicating a fault such as an open circuit elsewhere in the bias path or a component failure. Conversely: * **B) A "click" is heard when an ohmmeter is touched across loudspeaker terminals.** This is a normal test result, indicating the loudspeaker's voice coil is intact. The ohmmeter's small DC current causes the cone to move slightly. * **C) A voltage drop across the leads of a 47K ohm resistor in an intermediate frequency amplifier stage.** Resistors are designed to have a voltage drop across them when current flows. This is a normal and expected condition in a working circuit. * **D) The presence of an AC signal on the output of an audio frequency amplifier stage.** An audio frequency amplifier's purpose is to amplify AC audio signals. The presence of an amplified AC signal on its output, given a proper input, is a sign of normal operation, not a fault.