Options are: CPCTC
Congruent
vertical angles are congruent
If alternate interior angles are congruent then lines are parallel

1) because they are vertical angles

2) because SAS

3)  CPCTC

4) Converse of the Alternate Interior Angles

answer: option a.

step-by-step explanation:

you know that the quadrilateral opqr ( a four sided figure) is inscribed in circle. this means that all its vertices are on the circle.

then, by definition, the opposite angles of the quadrilateral are supplementary, this means that the sum of their measures is 180 degrees.

you can observe in the figure that the angles ∠opq   and the angle ∠orq   are opposite, therefore:

then, can be used to d to calculate the measure of ∠opq