Final answer:
The correct answer is option a) congruent, as both pairs of congruent opposite angles are defining characteristics of a parallelogram in a quadrilateral.
Step-by-step explanation:
If both pairs of opposite angles of a quadrilateral are congruent, then the quadrilateral is a parallelogram. This is due to one of the defining properties of a parallelogram, where opposite angles are of equal measure. To elaborate, in a quadrilateral, when one pair of opposite angles is congruent, it suggests that the sides of the quadrilateral are parallel, which is a trait of parallelograms.
However, this condition alone isn't sufficient to conclude that a quadrilateral is a parallelogram. When both pairs of opposite angles are congruent, it confirms that we have two sets of parallel sides, which validates the definition of a parallelogram.
In conclusion, the correct answer to the question is option a) congruent. This means that the opposite angles have the same measure, which is true for parallelograms but not necessarily true for other quadrilaterals, such as trapezoids or kites, unless they have additional specific properties.