Final answer:
The bases of a cylinder must be parallel and congruent discs.
Step-by-step explanation:
In a cylinder, the bases are the two circular shapes at the top and bottom of the cylinder. These bases are parallel because they are on the same plane and do not intersect with each other. They are also congruent, which means they have the same shape and size. In this case, the bases are discs because they are circular in shape.
Learn more about Cylinder bases and shapes