Select the correct mirror image of the given figure when the mirror is placed…

Concept: A mirror standing along the line PQ, which runs vertically beside the figure, produces a lateral inversion, that is, a reflection across a vertical axis. Left and right are exchanged while top and bottom are left untouched, and nothing is rotated or turned upside down. Two things therefore happen together in the image: the characters appear in the reverse of their original left-to-right order, and each individual character is itself flipped about its own vertical axis.

Application: The given figure reads F G H T K D from left to right, and the mirror line PQ stands vertically to the right of it, so the two steps of the reflection are applied in turn.

1. Reverse the left-to-right order of the six characters. F G H T K D read backwards gives D K T H G F.

2. Flip each of those characters about its own vertical axis. D becomes a D whose bowl opens towards the left. K becomes a K whose upright stroke stands on the right with both arms opening towards the left. T is symmetric about a vertical axis, so it is unchanged. H is symmetric in the same way, so it is unchanged. G becomes a reversed G whose opening faces left. F becomes a reversed F whose two arms extend towards the left.

Carrying out both steps gives the required image: the row that reads, from left to right, a reversed D, a reversed K, a T, an H, a reversed G and a reversed F.

Cross-check: comparing that requirement with the other rows shows where each of them departs from the reflection.

• A row that still opens with an upright F and keeps F, G, H, K and D in the order of the given figure has not carried out the first step at all, and a row that carries eight characters cannot be the image of a six-character figure, because a reflection never adds or removes characters.

• A row that opens with a reversed D and closes with a reversed F, but shows the K with its upright stroke on the left and both of its arms opening towards the right, has applied the second step to every character except that one: the flipping of each individual character about its own vertical axis was left out for the K alone, so the order is right while one character is not.

• A row that shows an L in third place or a three-barred E in last place has replaced characters of the given figure, and a reflection changes only the orientation and the order of characters, never their identity.