Which of the following is a validation of congruency between two polygons?
a) if by applying only rotation you can make them coincide
b) if by applying only translation you can make them coincide
c) if by applying rigid motions you can make them coincide
d) if by applying dilation you can make them equal

I think the correct answer would be C. A validation of congruency between two polygons would be that  if by applying rigid motions you can make them coincide. Two figures are said to be congruent if and only if these figures have the same shape and the same size. All of their sides and angles are the same. Rigid motion is a motion done to a figure that preserves distance or length. If all the rigid motions like rotation, reflection, translation and glide reflection are done and the figures are the same or the lengths are preserved, then the polygons should be congruent.