Use ΔPQR below to answer the question that follows: Triangle PQR with sides PR and QR intersected by segment ST.

Which fact is not used to prove that PQR is similar to STR?

Segments ST and PQ are parallel.
Angle P is congruent to itself due to the reflexive property.
RP is a transversal line passing ST and PQ.
Angles RTS and RQP are congruent due to the Corresponding Angles Theorem.