Some polyhedrons are neither prisms nor pyramids. a. true b. false

True.

Polyhedrons are closed figures which are bounded by polygons such as cube, prism, pyramids.

Non-polyhedrons are solid figure which have sides but are not polygons such as sphere, cone and cylinder.

Please see the attached figure for polyhedron:

Hence, the given statement is true i.e. other polyhedrons are present other than prisms and pyramids.