Which type of transformation is described as flipping an image across a specific axis?

The transformation described as flipping an image across a specific axis is known as a reflection. When an image is reflected, each point of the image is mirrored across a designated line (or axis), creating a symmetrical counterpart on the opposite side. This axis acts like a "mirror," allowing the original figure and its reflected image to remain congruent, meaning they are the same shape and size but positioned differently.

In contrast, translation involves sliding an image to a different position without altering its shape, size, or orientation. Rotation entails turning an image around a fixed point by a certain angle, preserving the shape and size but changing the orientation. Stretching refers to altering the size of an image in one direction, which distorts the original shape. Therefore, the only transformation among the choices that directly describes flipping across an axis is reflection.