Can a polyhedron have for its faces:
(i) 3 triangles?
(ii) 4 triangles?
(iii) a square and four triangles?
(i) No, because in order to complete a polyhedron, we need at least four triangular faces.
(ii) Yes, a polyhedron with 4 triangular faces is a tetrahedron.
(iii) Yes, with the help of a square bottom and four triangle faces, we can form a pyramid.