Final answer:
A cylinder is a three-dimensional shape with circular bases. In this case, it is divided into three sections with different diameters.
Step-by-step explanation:
A cylinder is a three-dimensional shape that has two circular bases and a curved surface connecting the bases. The diameter of a cylinder is the distance between two points on the circular base, passing through the center of the cylinder. In the given question, the cylinder is divided into three sections with diameters of 102 and 138 units.