Which statement about the cycle states is true?

• A. The refrigerant is always a vapor on the high pressure side.
• B. The metering device increases pressure.
• C. The evaporator input is high pressure liquid.
• D. The evaporator output is low pressure vapor.

Answer: (D)

The key idea is that the evaporator operates at low pressure and is where the refrigerant absorbs heat to change from liquid to vapor. The refrigerant entering the evaporator is a low‑pressure liquid that boils as it picks up heat from the surroundings, and the refrigerant leaving the evaporator is low‑pressure vapor that heads to the compressor. This is why the statement about the evaporator output being low‑pressure vapor is true. The other statements aren’t correct because the high‑pressure side isn’t always vapor (in the condenser it’s mostly liquid after condensation), the metering device lowers—not increases—pressure, and the evaporator input is not high‑pressure liquid.