You are correct, the answer B) higher than normal discharge pressure is the correct answer. An excessive charge of refrigerant in a thermostatically controlled, air-cooled, refrigeration system using a TXV as an expansion device will cause the discharge pressure to be higher than normal. This is because the excessive refrigerant charge increases the refrigerant density, which in turn increases the pressure in the high-pressure side of the system, including the compressor discharge. The other answer choices are incorrect because: A) the compressor would not run continuously, it would short-cycle due to the high discharge pressure, C) the box temperature would actually be lower than normal due to the excess refrigerant, and D) oil foaming in the compressor is not a direct result of an excessive refrigerant charge.