Geometry

Question Analysis:
This question tests fundamental understanding of diagonal properties in parallelograms.

Key Concept Explanation:
The defining property of parallelogram diagonals is that they bisect each other.

Step-by-Step Solution:
Recall that in any parallelogram, diagonals bisect each other
Therefore, AO must equal OC (and BO must equal OD)
Other properties (equality, perpendicularity) only apply to special parallelograms

Option Analysis:
A: Correct - universal property
B: Only true for r...