Which answer figure is the exact mirror image of the given sequence when a…

Concept. A vertical plane mirror held to the right of a horizontal string produces a reflection in which two changes happen together: (1) the order of the characters is reversed end-for-end, and (2) every individual character is inverted left-to-right (laterally flipped). A figure is the exact mirror image only if BOTH changes are present.

Application to pR4GTF7Dq.

1. Reverse the order. Reading pR4GTF7Dq from right to left gives the character sequence q, D, 7, F, T, G, 4, R, p.

2. Laterally flip each glyph. q becomes p; D becomes a back-to-front D (bowl on the left); 7 becomes a reversed 7; F becomes a reversed F; T stays T (it is symmetric about a vertical axis); G becomes a reversed G; 4 becomes a reversed 4; R becomes a reversed R; and the final p becomes q.

3. Read off the result. The exact mirror image therefore begins with an upright p, ends with an upright q, and in between shows a reversed-D, reversed-7, reversed-F, upright T, reversed-G, reversed-4 and reversed-R. This is the figure whose first character is p and last character is q with every interior glyph turned back-to-front.

Cross-check. Confirm both conditions on the end characters, which are the easiest to verify: the original starts with p, so the reflection must END with q (a true reflection swaps p and q). A figure that ends in an upright D and d, or that begins with q and ends with p, has reversed the order but failed to flip one or more glyphs, so it is not the exact mirror image.