Geometry

Question Analysis:
This question tests knowledge of valid triangle congruence postulates and asks which one does not guarantee congruence.

Key Concept Explanation:
SSS (Side-Side-Side): Congruent triangles if all three sides are equal.
ASA (Angle-Side-Angle): Congruent triangles if two angles and their included side are equal.
AAS (Angle-Angle-Side): Congruent triangles if two angles and a non-included side are equal.
SSA (Side-Side-Angle): Not always valid because it can create two different triangles (ambiguous case).

Step-by-Step Solution:
SSS, ASA, and AAS are all valid triangle congruence postulates.
SSA is not a valid congruence postulate because it can produce two different possible triangles (except in the right triangle HL case).
Therefore, the correct answer is C. SSA.

Option Analysis:
(A) SSS: Correct congruence rule.
(B) ASA: Correct congruence rule.
(C) SSA: Incorrect...