The correct answer is A) pressure relief device. According to 46 CFR Part 58, all refrigeration systems must be equipped with a pressure relief device to protect the system from over-pressurization and potential hazardous failures. The pressure relief device is a critical safety feature that allows the system to release excess pressure buildup, preventing the refrigeration system from rupturing or exploding. The other options are incorrect because they are not universally required for all refrigeration systems. A refrigerant receiver is not required for all systems, and low-pressure and high-pressure cut-outs, while important safety features, are not mandatory for all refrigeration systems under the 46 CFR regulations.