What shape has no straight edges, one vertex, and one circular base: cylinder, a cone, or a sphere?
And here we have our cylinder, our cone, and our sphere. We’re looking for a shape that has no straight edges. Could it be a sphere? A football is a sphere. Does it have any straight edges? Yes, a sphere has no straight edges. Our shape has one vertex. A sphere doesn’t have any vertices. So it can’t be the sphere.
Our shape has one circular base. The cylinder has two circular faces. So our shape can’t be the cylinder. The cone has one circular base. It also has one vertex. The cone appears to have two straight edges because we’ve drawn it as a 2D shape on paper. But the cone actually has just one circular edge, so no straight edges.
So we can say the shape which has no straight edges, one vertex and one circular base is the cone.