Select all transformations that maintain a shape's congruency.

a translation six units up

a reflection across the x-axis

a 180° rotation about the origin

a dilation with a scale factor of 2

a reflection across the y-axis and then a translation three units left

a translation two units down and then a dilation with a scale factor of less than 1

a reflection across the y-axis and then a dilation with a scale factor greater than 1