Geometry

Question Analysis:  
This question tests awareness of which steps are usually skipped.  
The main focus is on avoiding unnecessary work.

Key Concept Explanation:  
Angle measures are rarely needed except to show right angles.

Step-by-Step Solution:  
Coordinate proofs favor slope and distance; full angle measures are avoided.

Option Analysis:  
- A. Needed for parallelism and perpendicularity.  
- B. Needed for congruence.  
- C. Correct. Exact angles are unnecessary unless right angles.  
- D. Needed ...