Final answer:
Extinguishers in residential corridors must be spaced so that the travel distance does not exceed 75 feet, ensuring quick access in case of fire.
Step-by-step explanation:
The spacing requirement for extinguishers in resident corridors is that the travel distance to an extinguisher cannot exceed 75 feet. This requirement is based on safety regulations to ensure that in the event of a fire, occupants have quick access to firefighting equipment. The correct response to the question is c) 75 feet.