We can see why (B) is correct if we call that the front-to-back explanation relies on the false premise of images in mirrors having 3D properties, but the field-of-sight explanation does not have this problem, as it relies only on axis rotations.
(C), on the other hand, is incorrect because the field-of-sight view DOES take into account the POV and orientation of someone observing reflections in the mirror, as lines 7-10 tell us directly.
