On a Refrigerant System There Is Heavy Frost on the Expansion

Multiple Choice

On a refrigerant system there is heavy frost on the expansion vave inlet and low-side pressure is well below normal.Technician A says that the expansion valve is stuck in the open position could be the cause.Technician B says that a restricted expansion valve inet screan could be the cause.Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B