Which of the following best describes a cylinder?
a. a three dimensional solid consisting of two parallel congruent polygons and all the points between them.
b. a three dimensional solid made from two parallel and congruent discs not in the same plane and all the points between them.
c. a three dimensional solid consisting of a base, a point not in the same plane as the base, and all the points between them.
d. a three dimensional solid made from a pile of similar two dimensional circles that grow smaller as the solid gets taller until it reaches a point at the vertex

Hey there!

The shape being described in letter A is a prism. A prism has two polygonal shapes on either end that can be any shape consisting of three or more sides. This won't be your answer, since cylinders have circular bases on either side. 

The shape being described in letter B is a cylinder. Not sure why they needed to throw in the plane part, but this is the only answer that describes the bases as being circular (or, as they put it, discs). 

The shape being described in letter C is a pyramid. If a shape has a polygonal base and meets at a point at the other end, it will be a pyramid. Obviously, a pyramid only has one end, meaning that this isn't your answer. 

The shape being described in letter D is a cone. Again, if a shape has a base and meets at a point, it will be a pyramid. However, in the case of a cone, the base will be circular and the other side will meet at a point. The entire shape will be rounded where a pyramid would have edges. Again, not your answer. 

Your answer will be B. Hope this helped you out! :-)