The vertices of ΔABC are A (1, 5), B (3, 9), and C (5, 3). The vertices of ΔDEF are D (−3, 3), E (−2, 5), and F (−1, 2). Which conclusion is true about the triangles? The ratio of their corresponding sides is 1:3. They are congruent by the definition of congruence in terms of rigid motions. The ratio of their corresponding angles is 1:3. They are similar by the definition of similarity in terms of a dilation.