This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
Concerning pulse oximetry true is 
Select and explain. 
A. Oxyhemoglobin and deoxyhemoglobin light absorption is equal at the isobestic point of 660nm, B. Measurements are accurate in the presence of high levels of bilirubin, C. Measurements are accurate in presence of carboxyhaemoglobin, D. Measurements are accurate in presence of pigmented skin.
D: Measurements are accurate in presence of pigmented skin.
Answer: D: Measurements are accurate in presence of pigmented skin. 
Explanation: Light absorption of both oxy and deoxy haemoglobin is equal at isobestic point of 805 nm. Bilirubin, carboxyhemoglobin and methaemoglobin can affect the reading of pulse oximeter. Pigmented skin doesn’t influence the reading.