Final answer:
Option A). A pulse oximeter should be used to evaluate a baby's oxygenation if persistent central cyanosis is suspected. It measures the amount of oxygen in the blood by sending two different wavelengths of light through a thin part of the body, typically the finger, and measuring the absorption of light by oxygenated hemoglobin.
Step-by-step explanation:
A pulse oximeter should be used to assess a baby's oxygenation and identify any persistent central cyanosis. An instrument used to measure blood oxygen levels is the pulse oximeter. It measures the amount of light absorbed by oxygenated hemoglobin by passing two distinct light wavelengths through a thin portion of the body, usually the finger. The % saturation of this data is then displayed, with typical readings falling between 95 and 100 percent.