Which statement is true for a parallelogram?

In a parallelogram, one of the fundamental properties is that it has two pairs of parallel sides. This means that each pair of opposite sides is not only equal in length but also runs in the same direction and never intersects. This characteristic is pivotal to the definition of a parallelogram itself, distinguishing it from other quadrilaterals.

While it’s important to note that option B is true, the other statements do not hold true for all parallelograms. For example, while rectangles are a type of parallelogram where all angles are right angles, this is not a requirement for all parallelograms. Similarly, equilateral properties and equal diagonals only apply to specific types of parallelograms, such as rhombuses or rectangles, but not to all. Thus, the truth of the statement regarding the pairs of parallel sides is what makes it the correct choice in this context.