Answer:
"plane of symmetry"
Explanation:
A line that divides a figure into mirror images, is axis of symmetry.
Horizontal axis is the axis that is horizontal to the figure that divides the figure into two parts, top and bottom, from the middle.
A plane of symmetry is a plane that divides a 3d figure into mirror images.
A rotational place is an imaginary plane that is used to visualize the rotation of objects.
From the definitions above, "plane of symmetry" is the right choice.