Final answer:
In the equation 'C=Fd1', 'C' stands for the minimum required rated discharge capacity of the pressure relief valve device or fusible plug for a refrigerant-containing vessel, which is measured in BTU per minute.
Step-by-step explanation:
The symbol 'C' in the formula C=Fd1 is equal to the minimum required rated discharge capacity of the pressure relief valve device or fusible plug for a refrigerant-containing vessel. This capacity is measured in BTU per minute, so the correct answer would be option A) Btu/minute. The purpose of the pressure relief valve is to prevent the pressure from rising above a specified limit that could be dangerous and lead to system failure. Therefore, it is crucial to accurately calculate this discharge capacity to ensure the safety and efficiency of the refrigeration system.