To prove the two triangles congruent using the Angle-Side-Angle (ASA) congruence criterion, you need two angles and the side between them to be congruent in both triangles.
Given the choices, the one necessary piece of additional information would be:
∠DCE ≅ ∠DCQ
This is because proving that these angles are congruent gives you the second angle needed along with the shared side (DC) to establish the ASA congruence for the two triangles.