Final answer:
The correct term for the area a single searcher can evaluate at a time is d. Swathe. It's specific to search and rescue, differentiating it from other terms like swatch, point to point, and zone.
Step-by-step explanation:
The term that describes the area in which a single searcher can evaluate at any given time is d. Swathe. This is a common term used in fields such as search and rescue operations, and it refers to the strip of land that an individual or a team can search effectively. The term swatch typically refers to a sample of fabric, point to point can refer to a type of communication or navigation between two distinct points, and zone is a more general term that could represent any designated area within a larger region.