To prove that triangles \( \triangle ABC \) and \( \triangle A''B''C'' \) are congruent using the ASA (Angle-Side-Angle) criterion through rigid motions, we need to show that you can obtain one triangle from the other through a series of rotations and reflections.
From the information provided, the sequence of transformations needs to first align \( \triangle ABC \) with respect to the common point \( C \) and then position it correctly relative to triangle \( \triangle A''B''C'' \).
Let's consider the options provided to find the one that leads to congruence:
- Rotate \( \triangle ABC \) -90 degrees (clockwise) about vertex \( C \), and then reflect \( \triangle A'B'C' \) across \( CA' \).
- Rotate \( \triangle ABC \) -90 degrees (clockwise) about vertex \( C \), and then reflect \( \triangle A'B'C' \) across \( B'C' \).
- Rotate \( \triangle ABC \) 90 degrees (counterclockwise) about vertex \( C \), and then reflect \( \triangle A'B'C' \) across \( CA' \).
- Rotate \( \triangle ABC \) 360 degrees (counterclockwise), and then reflect \( \triangle A'B'C' \) across \( B'C' \).
The most reasonable transformation that aligns \( \triangle ABC \) with \( \triangle A''B''C'' \) while keeping \( C \) fixed involves both a suitable rotation and a reflection. The rotation should orient the triangles appropriately, and the reflection should then correctly align them.
Looking through the options, the correct transformation is:
Rotate \( \triangle ABC \) -90 degrees (clockwise) about vertex \( C \), and then reflect \( \triangle A'B'C' \) across \( CA' \).
This is the first option. By rotating triangle \( ABC \) and reflecting it across \( CA' \), we effectively demonstrate the congruence condition under the specifications of ASA congruence.