Which properties are characteristic of a parallelogram?

A parallelogram is defined by specific properties that distinguish it from other quadrilaterals. One of the defining characteristics is that opposite sides are parallel. This means that if you extend the two opposite sides, they will never intersect, maintaining a consistent distance apart. Additionally, in a parallelogram, opposite angles are congruent, meaning that the angles that are across from each other in the figure have the same measure. These two properties—parallel opposite sides and congruent opposite angles—are fundamental to the definition of a parallelogram.

In contrast, the other options present attributes that apply to different types of quadrilaterals. For example, having all angles as right angles and diagonals that are equal describes a rectangle, not a general parallelogram. The property of having all sides congruent and diagonals that are perpendicular is specific to a rhombus. Lastly, stating that there is exactly one pair of parallel sides is indicative of a trapezoid, not a parallelogram, since a parallelogram requires two pairs of parallel sides.

Therefore, the properties of opposite sides being parallel and opposite angles being congruent truly encapsulate what defines a parallelogram.