Question

Prove that if two angles are complementary to the same angle then they are equal in measure.
1: ∠1 is complementary to ∠2 and ∠3 is complementary to ∠2.
2: m∠1 + m∠2 = 90 and m∠3 + m∠2 = 90
3: m∠1 + m∠2 = m∠3 + m∠2
4: m∠1 = m∠3

A: Definition of complementary
B: Given
C: Subtraction property of equality
D: Substitution

Answer 1

I think 2 is D