The correct answer is C. According to 46 CFR regulations, to initiate a safety shutdown on an automatic auxiliary boiler, the fuel pressure must be lowered to a value below what is required for safe combustion. After the safety shutdown, a manual reset must be required before the boiler can be restarted. This ensures that the boiler system is thoroughly checked and reset before resuming operation, enhancing safety. The other options are incorrect because they do not accurately reflect the regulatory requirements. Raising the fuel pressure above the safe limit (option A), or automatically restarting the boiler after a shutdown (options A and D), would not provide the necessary safety checks and controls required by the regulations.