How come when you look into a mirror right becomes left but up never becomes down?

The image of everything in front of the mirror is reflected backward, retracing the path it traveled to get there. Nothing is switching left to right or up-down. Instead, it's being inverted front to back. That reflection represents the photons of light, bouncing back in the same direction from which they came.

Explanation:

Mirrors don’t reverse left and right. That’s just our interpretation of what happens. Your reflection in the mirror is actually reversed front to back, if you have a mole on the left side of your face, it still appears on the left side of the reflection. But we are used to seeing the faces of other people and we instinctively perform the mental rotation because we know that they have turned through 180 degrees to face us. The image in the mirror is reflected, not rotated, so when we rotate it back in our head, it appears reversed.

b. failure at least that one seems the most negative out of all of the answers provided pls correct me if i'm wrong. : ))