The correct answer is A) "2" should be turned to further compress the spring. The device shown in the illustration is a pressure regulating valve, which is used to control the operating head pressure of the refrigeration system. Increasing the compression of the spring ("2") will increase the operating head pressure, as it will require more pressure to overcome the spring force before the valve opens and allows refrigerant to flow. This is the correct way to increase the operating head pressure using this type of device. The other options are incorrect because: B) Relaxing the spring compression would decrease the operating head pressure; C) Compressing the bellows would not directly affect the operating head pressure; and D) Relaxing the bellows would not increase the operating head pressure.