Answer :

To determine whether a trapezoid is defined as a quadrilateral with exactly one pair of parallel sides, let's break down the definitions step-by-step.

1. Quadrilateral: A quadrilateral is a polygon with four sides and four angles.

2. Trapezoid: We need to clarify whether a trapezoid fits a specific characteristic regarding its sides.

Considering the definition:
- A trapezoid traditionally in many regions (including the United States) is defined as a quadrilateral with exactly one pair of parallel sides.
- The parallel sides of the trapezoid are called the bases, while the non-parallel sides are called the legs.

Therefore, given the definition in our problem, a trapezoid indeed is a quadrilateral that has one and only one pair of parallel sides.

So:
A. True