Final answer:
The OTA locking the brakes on a wheelchair during patient transfer exemplifies the ethical principle of nonmaleficence, which emphasizes avoiding harm and ensuring patient safety.
Step-by-step explanation:
When an entry-level Occupational Therapy Assistant (OTA) is observed locking the brakes on a wheelchair during patient transfer to a raised toilet seat, the ethical principle most clearly demonstrated is nonmaleficence. This principle is centered on the concept of not doing harm and ensuring the safety of the patient. By locking the wheelchair brakes, the OTA is taking a precautionary measure to prevent the wheelchair from moving unexpectedly, which could potentially cause the patient to fall or become injured. This responsible action reflects the OTA's commitment to the principle of nonmaleficence, ensuring that the patient's safety is a top priority during the transfer process.