Given: m || n and p is a transversal
prove: m2 = m7

what is the missing reason in the proof?

statement reason
1. m || n and p is a transversal 1. given
2. ∠2 ≅ ∠3 2. ver. ∠s theroem
3. m∠2 = m∠3 3. def. of congruent
4. ∠3 ≅ ∠7 4. corr. ∠s theroem
5. m∠3 = m∠7 5. def. of congruent
6. m∠2 = m∠7 6. ?
a. corresponding angles theorem
b. alternate interior angles theorem
c. transitive property
d. subtraction property