Final answer:
The most likely cause for not getting a pulse oximetry reading is incorrect probe placement option (a).
Step-by-step explanation:
The most likely cause for a CPCT not being able to get a pulse oximetry reading on the monitor is incorrect placement of the probe option (a). The pulse oximeter probe needs to be properly attached to the patient's finger or earlobe for accurate measurements. Other factors such as high blood pressure, normal oxygen saturation, or dehydration are not typically associated with the inability to get a reading on the monitor.
If the CPCT cannot get the pulse oximetry reading to appear on the monitor, it could be due to the incorrect placement of the probe.