High suction pressure accompanied by low suction temperature to a refrigeration system compressor is caused by which of the following?

Correct Answer: Option D — the expansion valve being open too wide

An excessively wide thermostatic expansion valve floods the evaporator with liquid refrigerant. This prevents complete vaporization, causing unboiled liquid to boil off in the suction line, which drops suction temperature while raising suction pressure due to the increased mass flow and volume.