Final answer:
The question seeks the pressure of R12 refrigerant at room temperature when the refrigeration machine is idle, which would require consulting an R12 pressure-temperature chart.OPTION A.
Step-by-step explanation:
The question is asking for the refrigerant pressure of an R12 (Freon-12) refrigeration machine at 72 F (approximately 22.22 C) while the machine is not running. Refrigerant pressure is dependent on temperature, and a pressure-temperature chart or a refrigerant pressure gauge can be used to determine the refrigerant pressure at a specific temperature.
As Freon-12 has a boiling point of -29.8 C, it is a gas at room temperature (25 C), and similarly at 72 F. Without the specific room temperature pressure data for R12, we can't provide an exact answer from the options given. As this seems to be a hypothetical or textbook question, the correct answer would typically be found on an R12 pressure-temperature chart referenced by HVAC technicians for the temperature in question.