The bases for a cylinder must be parallel and congruent _____.A.polygonsB.rectanglesC.discsD.squares

The bases of a cylinder are defined as two surfaces that are parallel and congruent to each other. This means that the shape of the bases must be exactly the same and lie in parallel planes.

In the case of a cylinder, the bases are circular in shape, which fits the definition of congruent discs. Thus, the correct answer to the question is:

C. discs

To elaborate, while all the options presented (polygons, rectangles, discs, squares) can represent shapes, only discs (which are essentially circular shapes) can form the bases of a cylinder. Rectangles and squares cannot create the three-dimensional shape characteristic of a cylinder, as these would lead to a prism with rectangular or square bases instead. Hence, the critical aspect is recognizing that the bases of a cylinder must be round, hence congruent discs.