Final answer:
The correct answer is as often as needed. The purpose of a safety valve on a high pressure boiler is to release excess pressure and prevent the boiler from exploding. It should be popped when the pressure exceeds the maximum allowable working pressure of the boiler.
Step-by-step explanation:
The correct answer is a) as often as needed. The purpose of a safety valve on a high pressure boiler is to release excess pressure and prevent the boiler from exploding. The valve should be popped when the pressure exceeds the maximum allowable working pressure of the boiler. This can happen at any time, so it is important to regularly monitor the pressure and pop the safety valve whenever necessary.