Final answer:
Patients have the right to refuse medical treatment at any time based on the principle of autonomy, which ensures their self-determination in healthcare decisions.
Step-by-step explanation:
The correct statement regarding a patient's consent to treatment is that patients may refuse treatment at any time, even if treatment has begun. The principle of autonomy ensures a patient's right to self-determination in healthcare choices, allowing them to grant or revoke consent for medical treatment at any stage. This principle is essential across various medical professions, from EMTs to paramedics, and is not restricted to any single type of healthcare provider.