A hemisphere is one example.
Cone or a pyramid
a two dimensional figure is flat. it only has length and width. three dimensional figures have length, width and height. A square is a 2 dimensional figure, but a cube is a 3 dimensional figure.
It is a sphere which looks like a globe
A polygon is a 2-dimensional closed figure that has at least three sides. A pentagon is a 2-dimensional closed figure that has five and only five sides, so it is a kind of polygon.
Because the base of a cone is round, it is the only three dimensional figure with only one vertex.
pyramid or cone
A hemisphere is one example.
Cone or a pyramid
No. Polyhedra are three-dimensional objects, and the base of any prism, strictly speaking, should be two-dimensional. Any convex polygon (which is two-dimensional) can form the base of a pyramid. A circle, which is technically not a polygon, is the only convex two-dimensional figure that cannot form the base of a pyramid because it forms the base of a cone.
a two dimensional figure is flat. it only has length and width. three dimensional figures have length, width and height. A square is a 2 dimensional figure, but a cube is a 3 dimensional figure.
...All polyhedrons
It is a sphere which looks like a globe
A 3D figure shows length, width and depth. While a 2D figure only shows length and width.
A polygon is a 2-dimensional closed figure that has at least three sides. A pentagon is a 2-dimensional closed figure that has five and only five sides, so it is a kind of polygon.
A closed three-dimensional figure formed by four or more polygons that intersect only at their edges is called a polyhedron. It contains flat faces, straight edges, and sharp corners or vertices.
Because that is how a polyhedron is defined.