B is incorrect because a parallelogram doesn't necessarily have congruent sides, it just has sides that are parallel. C is incorrect because a rectangle has a pair of sides longer than the other pair of sides. D is wrong because of the reason listed under C.
A RHOMBUS and SQUARE are both quadrilaterals that have four congruent sides. By definition, parallelograms have to have two sets of congruent sides, and so do rectangles. Though parallelograms can have four congruent sides, they are not always; rectangles never have four congruent sides.
