A quadrilateral with one pair of parallel side is a A) ParallelogramB) SquareC) RectangleD) Trapezium

The correct answer is D) Trapezium.

Explanation:
A trapezium (also known as a trapezoid in some regions) is a type of quadrilateral that has exactly one pair of opposite sides parallel. The defining characteristic of a trapezium is the parallelism of one pair of sides, while the other pair is not parallel.

Parallelogram: A parallelogram has two pairs of opposite sides that are parallel.
Square: A square is a type of parallelogram, and all its sides are equal and opposite sides are parallel.
Rectangle: A rectangle is a type of parallelogram where opposite sides are parallel, and all angles are 90 degrees.
Trapezium: A trapezium only has one pair of opposite sides that are parallel, fitting the description in the question.
Thus, the correct choice is D) Trapezium.