Answer: A. All parallelograms have opposite sides that are parallel.
Explanation:
A. All parallelograms have opposite sides that are parallel.
✓ True
B. Some parallelograms have side lengths that are all different.
✗ False, they are congruent.
C. Some parallelograms have more than 4 sides.
✗ False. All parallelograms are quadrilaterals, shapes with 4 sides.
D. All parallelograms have 4 square corners.
✗ False. While they have 4 corners, they are not "square corners" - right angles.