Question

each picture shows a figure and its reflection. which picture shows the line of reflection?
look for the line of reflection that you can flip the glove across to make a mirror image.

Explanation:

The line of reflection must be the axis where flipping the original figure across it creates an exact mirror image (reflection). For the top-left image, the horizontal line between the gloves: flipping the top glove over this line results in the bottom glove, which is a perfect mirror reflection (matching orientation as a reflection). The other images either have lines that don't produce a mirror image (top-right: gloves are identical, not reflections; bottom-left: vertical line through gloves doesn't create a mirror flip; bottom-right: vertical line outside doesn't map one glove to the other as a reflection).

Answer:

The top-left picture (with the horizontal red line between the two gloves) shows the line of reflection.