The table contains the proof of the relationship between the slopes of two perpendicular lines. What is the reason for statement 2? A. Parallel line segments that meet a common perpendicular line are proportional in length. B. The lengths of vertical and horizontal sides in congruent triangles are in a common ratio. C. Trigonometric identities determine the lengths of the legs in a right triangle. D. Corresponding side lengths in similar triangles are proportional in length.