Select all the sequences of transformations that always maintain congruence. a reflection and then a translation a translation and then a rotation a rotation and then a reflection a dilation and then a reflection a rotation and then a dilation a translation and then a dilation

A reflection followed by translation, a translation followed by rotation, and a rotation followed by reflection all preserve congruence.

Anything that changes the size of the figure does not preserve congruence.  The other three choices all have a dilation in them; a dilation changes the size of a figure.  Therefore it does not preserve congruence.