Final answer:
A trapezoid is a quadrilateral with one pair of parallel sides, making option A the correct answer.
Step-by-step explanation:
A trapezoid is a quadrilateral with exactly one pair of parallel sides. The other two sides may or may not be parallel. This means that option A is the correct answer, as a trapezoid can have one or more pairs of parallel sides.
Learn more about Properties of Trapezoids