Triangles PQR and XYZ are right-angled at Q and Y respectively. If PR=XZ and QR=YZ, which statement about their congruence is correct?
(a) They are congruent by SAS.
(b) They are not congruent because only one side is equal.
(c) They are congruent by RHS.
(d) They are congruent by ASA.