The two-column proof below describes the statements and reasons for proving that corresponding angles are congruent:

what is the missing statement for step 5?

a. m∠sqv + m∠vqt = 180°

b. m∠sqv = m∠sqt

c. m∠sqv + m∠sqt = m∠vqt

d. m∠sqv + m∠sqt = 180°

step statements reasons
1 segment uv is parallel to segment wz given

2 points s, q, r, and t all lie on the same line. given

3 m∠sqt = 180° definition of a straight angle

4 m∠sqv + m∠vqt = m∠sqt angle addition postulate

5 substitution property of equality

6 m∠vqt + m∠zrs = 180° same-side interior angles theorem

7 m∠sqv + m∠vqt = m∠vqt + m∠zrs substitution property of equality

8 m∠sqv + m∠vqt − m∠vqt = m∠vqt + m∠zrs − m∠vqt
m∠sqv = m∠zrs subtraction property of equality
∠sqv ≅ ∠zrs definition of congruency