General Studies · Spatial Aptitude

An art gallery plan consists of an inner shaded polygonal region with opaque boundary walls. A security guard posted at a single fixed location has a 360° stationary view. If the guard can see every point of the inner space from that position, and the valid candidates among labeled positions are P, Q, R, and S, where Q and S have full line-of-sight to all corners while P and R are obstructed by inner walls, which one of the following correctly represents the set of ALL possible locations where the guard can be posted?