Hello, fecoupefe!

The question is too vague . . .The question is: which shapes have circular cross-sections?

My child has said: cone, sphere and a cylinder.

A sphere has a circular cross-section no matter at what angle the plane cuts the sphere.

A cone has a circular cross-sectionifthe plane is perpendicular to its axis.

The same is true for a cylinder . . . or an hourglass . . . or a cable.

Take a king-size bedsheet and push it halfway through a napkin ring.

We have a "shape" that has one circular cross-section.

Does that count?