What position describes someone lying face up?

The correct choice describes someone lying face up as the supine position. This term is commonly used in anatomy and medicine to refer to the orientation of the body when an individual is on their back with their face directed upwards. This position is often utilized in various medical assessments and procedures because it allows for easier access to certain areas of the body, such as the thorax and abdomen.

Conversely, the prone position refers to a face-down orientation, while the lateral position indicates that a person is lying on their side. The vertical position implies an upright stance, which does not fit the description of lying down. Understanding these terms is crucial in contexts such as medical training, forensic investigations, and ensuring clear communication in clinical settings.