Watershed stroke occurs in which of the following areas?

Watershed strokes occur in regions of the brain that lie between two major cerebral arteries, often referred to as "border zones." These areas are particularly vulnerable to ischemia because they are at the periphery of the blood supply from the major cerebral arteries. When blood flow is compromised, either due to systemic hypoperfusion or occlusion of one of the supplying arteries, these watershed areas may not receive adequate blood supply, leading to a stroke in those regions.

In contrast, the other options do not correspond to the characteristics of watershed strokes. For example, strokes within the brainstem involve different vascular territories and mechanisms that are not related to watershed areas. Similarly, strokes that occur in the cerebellum or within a single cerebral artery are more directly associated with the specific artery supplying that region, rather than the junctional areas between arteries where watershed strokes are commonly seen.