Geometry

Question Analysis:
This question tests understanding of core indirect proof techniques.

Key Concept Explanation:
Contrapositive (A): A logical equivalent of the original statement.
Contradiction (B): Assumes the negation of the conclusion to derive an impossibility.
Distractors: C (direct proof), D (empirical verification), and E (illogical assumption) are invalid for indirect proofs.

Step-by-Step Solution:
Contrapositive (A): Valid as it logically mirrors the original statement.
Contradiction (B): Valid by definition of indirect proof.
Other Options:
C: Direct method, not indirect...