Correct answer is (b) By Pulse Oximetry
Best explanation: Pulse Oximetry is used to measure the oxygen saturation of the blood. In this process, light a light and a detector is used. It is normally in a band or a clip with the light source and the detector at the opposite ends. The light is projected at the finger and it is detected on the nail side. The light has an absorbance ratio which determines the amount of oxygen that is present in the blood.