Answer:
C.
Step-by-step explanation:
ASA stands for angle-side-angle.
one side and the 2 angles at the end points of this side are known. only one triangle can be created with that information.
and that is our situation here.
the sides PQ and respectively ST are known (the fact that they are of equal length qualifies for that).
and the angles at the end points of PQ are known (again, the fact that they have the same size as the angles for ST qualifies for that too).
so, ASA applies to prove that both triangles are congruent.