Triangles A B C and Q R S are shown. Sides A B and Q R are congruent. Angles C A B and R Q S are congruent. Angles Q S R and A C B are congruent.

Two rigid transformations are used to map TriangleABC to TriangleQRS. The first is a translation of vertex B to vertex R. What is the second transformation?

a reflection across the line containing AB

a rotation about point B

a reflection across the line containing CB

a rotation about point C