Explanation: This question describes the operation of a specific auto-alarm system, which historically were specialized devices used in maritime radio for detecting distress signals, not a standard piece of amateur radio equipment. However, the question tests understanding of basic fail-safe design principles in electronic systems. An "open filament" signifies a component failure (e.g., in a vacuum tube, if present). In critical alarm systems, a failure is often designed to trigger an alarm rather than silently fail. This is known as a fail-safe mechanism. If the system is designed with a fail-safe mechanism: * An open filament would indeed cause a circuit to fail, likely de-energizing a crucial relay like K-105. * The de-energization of K-105 could then apply voltage to a time-delay relay, K-100, initiating a sequence. * Finally, another relay (K106) in the sequence would activate an audible alarm, such as a bell, after a programmed delay (e.g., 2 minutes). Since all options describe a plausible sequence of events for a fail-safe auto-alarm system responding to a component failure, all actions would occur.