Option D:
SAS
Solution:
Given
To prove that
In ΔPQR and ΔRSP,
(given side)
(given)
By alternative interior angle theorem,
∠PRS ≅ ∠QPR (angle)
By reflexive property of congruence,
(side)
Hence by Side-Angle-Side (SAS) congruence rule,
ΔPQR ≅ ΔRSP
Option D is the correct answer.
Hence the missing reason is SAS.