Geometry

Question Analysis:
This question focuses on recognizing a valid proof method, not just a property.
The main focus is understanding what counts as sufficient evidence to prove a parallelogram.

Key Concept Explanation:
One of the five ways to prove a quadrilateral is a parallelogram is by showing one pair of opposite sides is both parallel and congruent.

Step-by-Step Solution:
Option A directly matches the known theorem
It gives both the direction (parallel) and length (congruent) of one side pair
Therefore, it is sufficient to prove a parallelogram

Option Analysis:
A. Correct – Matches a known valid proof method
B. Diagonals at right angles don’t prove a parallelogram – that fits kites
C. One pair of angles isn’t enough – ...