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