Final answer:
The supine position in a medical examination is when a person is lying on their back with their face up, which is different from the prone position where a person lies face down.
Step-by-step explanation:
The supine position in a medical examination is described as A) Lying on the back with the face up. When a body is lying down, it can be positioned as either prone or supine. The term prone describes a face-down orientation, while supine describes a face-up orientation. These terms are integral when discussing the anatomical position of the body during physical examinations or surgical procedures. Understanding the distinction between supine and prone is also central to studying systemic anatomy and observing the structures within the thoracic cavity, such as the heart and lungs.