Question

13 in parallelograms, opposite sides are . perpendicular parallel supplementary

Explanation:

A parallelogram is defined as a quadrilateral with two pairs of parallel sides. The property of having opposite sides parallel is fundamental to the definition of a parallelogram. Perpendicular means at right angles (90 degrees), which is not a general property of all parallelograms (only for special ones like rectangles). Supplementary refers to angles adding up to 180 degrees, which is about angles, not sides.

Answer:

parallel