The thermostatic expansion valve in a refrigeration system further opens when the diaphragm flexes downward. With all other conditions being the same, what single condition causes this?

Correct Answer: Option C — an increase in sensing bulb temperature

An increase in sensing bulb temperature raises the internal vapor pressure within the power element, pushing downward on the diaphragm. This action overcomes the opposing evaporator pressure and spring force, driving the valve open to increase refrigerant flow.