Janet is designing a frame for a client. She wants to prove to her client that m∠AGE ≅ m∠CHE in her sketch. What is the missing justification in the proof?

Segment AB is parallel to segment CD, and transversal EF intersects segment AB at G and segment CD at H.

Statement Justification
segment AB is parallel to segment CD with transversal segment EF Given
m∠AGE ≅ m∠HGB Vertical Angles Theorem
m∠HGB ≅ m∠CHE Alternate Interior Angles Theorem
m∠AGE ≅ m∠CHE
Alternate Exterior Angles Theorem
Corresponding Angles Theorem
Reflexive Property
Transitive Property

The missing justification in the proof is the Alternate Exterior Angles Theorem.