Answer:
A//Triangle RQS
Explanation:
B and C are the same (STQ and QST) so it's likely not those.
This leaves us with SPR and RQS.
For the triangles to be similar the only detail that can be changed is size (Angle degrees, shape, etc. can't be changed).
With that context Triangle PQR is an obtuse triangle while triangle SPR is a right triangle therefore the angle degrees are changed.
Using process of elimination the answer is A. Triangle RQS
I hope this is good!