A secondary power supply system for a fire detection and alarm system must be able to make the system fully operational within:

A. 10 seconds of the main power supply's failure.
B. 30 seconds of the main power supply's failure.
C. 60 seconds of the main power supply's failure.
D. 90 seconds of the main power supply's failure.

Answer: B. 30 seconds of the main power supply's failure.