The author doesn’t discuss imagined objects. Although she refers to an “imagined space” in a mirror, this isn’t the same concept as an imagined object. Since (A) doesn’t occur, it can’t be the purpose of the line we’re asked about.

The author never suggests that it’s “impossible” to perceive reflected objects without using mental constructs. The author mentions earlier that we’re accustomed to dealing with mental constructs rather than sense perceptions, but this doesn’t imply that we need to use mental constructs in order to perceive images of reflected objects. Since (B) doesn’t occur, it can’t be the purpose of the line we’re asked about.

This best captures the point expressed in the line immediately before the line we’re asked about. The line we’re asked about is supposed to be an example of the point made in the previous line. That point is that mirrors don’t actually present images with depth. The images appear to be three-dimensional, but this is an illusion.

Although the author does state earlier in P3 that we typically deal directly with mental constructs, the line we’re asked about isn’t designed to illustrate that claim. How do we know this? Because when the author uses the phrase “for example” to introduce the line we’re asked about, that indicates we’re about to get an example of the immediately preceding line. The immediately preceding line is about mirrors showing an image that appears to have depth.

It’s not clear that perceiving an object’s image as having depth constitutes a change in the “shape” of the perceived object. In any case, the lack of focus our eyes give to mirrors isn’t a “psychological activity.” Whether we’re focusing our eyes on something isn’t related to our mental or emotional state or our thoughts.