Assertion (A): Large cold storage plants use ammonia as refrigerant while domestic refrigerators use chlorofluorocarbons. Reason (R): Ammonia can be liquified at ambient temperatures at low pressures.

Assertion (A): Large cold storage plants historically and often still use ammonia as a refrigerant due to its high efficiency and low cost, despite its toxicity and flammability, which require strict safety protocols. Domestic refrigerators historically used CFCs (like R-12) which were non-toxic and non-flammable, making them safer for homes, though environmentally harmful (now largely replaced by HFCs, HCFCs, isobutane, etc.). Thus, the assertion holds as a general historical and technical distinction. Reason (R): Ammonia requires significant pressure to be liquefied at ambient temperatures. For example, at 25°C, the saturation pressure of ammonia is around 10 bar (approximately 1 MPa or 145 psi), which is not considered "low pressure". The statement that ammonia can be liquefied at ambient temperatures at low pressures is factually incorrect.