Answer:The fact '
is congruent to itself due to reflexive property' is not used to prove that

Explanation:
Here we have a triangle PQR in which ST is the line segment which joins the points S and T where
and

Now let

And, here PR is the common transversal which passes through the parallel lines ST and PQ.
So, In triangles PQR and STR,
( reflexive )
( by corresponding angle postulate)
Thus,
( by AA postulate of similarity)
Therefore, from the above proof we can say that except the fact '
is congruent to itself' we are using all the given options.