Janet is designing a frame for a client. She wants to prove to her client that m∠1 = m∠3 in her sketch. What is the missing justification in the proof? Segment CD intersects segment AB, creating angles 1, 2, 3, and 4. Statement Justification Segment CD intersects segment AB Given ∠1 + ∠ 2 = 180° ∠ 2 + ∠3 = 180° ∠1 + ∠ 2 = ∠ 2 + ∠3 Transitive Property ∠1 = ∠3 Subtraction Property Definition of Supplementary Angles Intersecting Lines Postulate Same-Side Interior Angles Theorem Vertical Angles Theorem