Jill cut out shape AEFB, folded it in half along the dashed line, and verified that figure ABCD and figure EFCD are congruent.

Which transformation describes how Jill proved that figure ABCD and figure EFCD are congruent?

A.
a translation 2 units to the right

B.
a 270° clockwise rotation around point C

C.
a reflection across line segment CD

D.
a reflection across line segment AB