Final answer:
The fire alarm circuits must operate for a minimum of 20 minutes in order to provide adequate and timely notification of an emergency.
Step-by-step explanation:
The correct answer is 3) 20 minutes.
In the context of fire alarm circuits, survivability refers to the ability of the circuits to continue operating during a fire or other emergency situation. To ensure the safety of occupants, fire alarm circuits must be designed to operate for a specified duration in order to provide adequate and timely notification of an emergency.
In this case, survivability means that the fire alarm circuits must continue to operate for a minimum of 20 minutes. This ensures that there is enough time for occupants to safely evacuate the building and for emergency response teams to arrive.