Which theorems or postulates allow you to find the value of y?

Vertical Angles Theorem and Triangle Angle-Sum Theorem

Below are the choices that can be found elsewhere:

a) vertical angles theorem and triangle angle-sum theorem

b) triangle exterior angles theorem and vertical angles theorem

c) triangles angle-sum theorem and angles addition postulate

d) angles addition postulate and triangles exterior angles theorem

The answer is C which is "triangles angle-sum theorem and angles addition postulate"