To prove that triangles \( \triangle ABC \cong \triangle QRS \) using the Angle-Side-Angle (ASA) postulate, you need to have two angles and the included side (the side between the two angles) congruent.
Given the options presented:
- \( \angle A \cong \angle Q \)
- \( \angle C \cong \angle S \)
- \( AC \cong QS \)
You would need the measures of two angles and the side between them to be congruent. If you already have \( \angle A \cong \angle Q \) and \( \angle C \cong \angle S \), you are missing the information about the included side, which is side \( AC \) and side \( QS \) in this context.
From the provided choices, the correct additional information needed would be:
\( AC \cong QS \)
Because this ensures you have two angles and the included side congruent, which satisfies the ASA criteria for triangle congruence.
Correct Answer: \( AC \cong QS \)