In this case, since the lengths of the sides of the similar figure are twice the lengths of the corresponding sides of the original figure, the transformation that takes place is a dilation.
A dilation is a transformation that alters the size of a figure while maintaining its shape, typically characterized by a center of dilation and a scale factor. Since the new figure has sides that are twice the length of the original, the scale factor is 2.
So, the correct response is dilation.