Final answer:
It is never (option a) appropriate to bypass a safety limit on a gas furnace as this violates safety regulations and puts lives and property at risk. Faulty limits should be replaced by qualified professionals without bypassing.
Step-by-step explanation:
The question revolves around the safety guidelines for handling gas furnaces which is a matter of concern in the engineering and technician practices. Specifically, it asks about the appropriateness of bypassing a safety limit on a gas furnace. The correct answer to this question is a) Never. Safety limits are put in place on gas furnaces to prevent dangerous conditions, such as overheating or gas leaks, which could lead to fires, explosions, or carbon monoxide poisoning.
These safety mechanisms are critical for the safe operation of the furnace, and bypassing them would not only violate safety regulations but also endanger lives and property. It's important to stress that even if the limit is faulty and needs replacement (d), it should not be bypassed; rather, the furnace should be shut down until the necessary repairs are made by a qualified professional.