The correct reason for why two triangles are similar if two corresponding interior angles are congruent is:
b. since the sum of angle measures in a triangle is 180°, the third angle pair must have the same measure and are thus congruent. because all three corresponding interior angles of the triangle are congruent, the triangles are similar by the definition of similarity.
This option correctly states that the sum of the angles in a triangle is 180 degrees, which leads to the conclusion that the third angles are also congruent. As a result, all three angles in the triangles are congruent, fulfilling the criteria for similarity (AA criterion: Angle-Angle similarity).