The correct answer is B. To determine the amount of superheat present in the suction gas leaving the evaporator coil, you need to note the low side pressure, determine the corresponding saturation temperature, and then subtract that saturation temperature from the temperature measured with a thermometer at the thermostatic expansion valve sensing bulb. This gives you the amount of superheat. The other options are incorrect because: A) This method would add the saturation temperature to the temperature at the sensing bulb, which would not give you the superheat. C) Subtracting the saturation temperature from the temperature at the compressor suction inlet would not provide the superheat at the evaporator coil. D) Subtracting the sensing bulb temperature from the saturation temperature would give you the subcooling, not the superheat.