Answer:
The correct option is 3.
Explanation:
Given information: Segments PQ and RS which intersect at point T. Segment PR is parallel to segment SQ.
Two triangles are called similar triangles if all the corresponding sides are proportional or all the corresponding angles are congruent.
In triangle PTR and triangle QTS,
(Alternate interior angles)
(Alternate interior angles)
(Vertically opposite angles)
By AA rule of similarity,

Therefore the fact "Angle PTR is congruent to angle QTS because they are vertical angles" is used to prove that triangle PTR is similar to triangle QTS.
Third option is correct.