Final answer:
The safety relief pressure should not be more than 6% below the design pressure for pressures above 250lbs P.S.I.
Step-by-step explanation:
The correct answer is c) 6% above or 6%. For pressure above 250lbs P.S.I., the safety relief shall not have a pressure more than 6% below that for which it is designed. This means that if the safety relief is designed for a certain pressure, it should not have a pressure that is lower than 6% below that design pressure when the pressure exceeds 250lbs P.S.I.