Chan is working on a proof that consecutive interior angles are supplementary.

1. m∠A+m∠C=180° Linear pairs are supplementary
2. m∠A=m∠E fill the blank
3. m∠E+m∠C=180° Substitution
4. ∠E and ∠C are supplementary Definition of Supplementary Angles
What is the missing reason in the proof?
Definition of Congruence
Transitive Property of Equality
Vertical Angles Theorem
Corresponding Angles Postulate