Question

select the image that is not a polyhedron.

Explanation:

A polyhedron is a 3 - D shape with flat polygonal faces, straight edges, and sharp vertices. The first image (a triangular pyramid) has triangular faces. The second image (a parallelepiped) has parallelogram - like faces. The fourth image has polygonal faces. However, the cylinder has curved surfaces (the lateral surface is curved), which do not meet the criteria of a polyhedron.

Answer:

The cylinder (the third image) is not a polyhedron.