a pentagonal pyramid it has five triangular sides that all meet at a point at the top. the base is a pentagon
Pyramid.
The answer is a pyramid.
None it is impossible.
The figure is a pyramid and the base is a square.
There is a contradiction in your question. If the base has four equal sides then is it a square so not all the faces are Triangles. However if the base is a square and the rest of the faces are triangles then your object is a "Square-based Pyramid"
A tetrahedron.
octagonal pyramid
TetrahedronEhm, I believe the answer would be a pyramid.
A pyramid with a triangular base. The faces are 4 equilateral triangles.
A regular pentagon-based pyramid.
Not necessarily. The solid could be a square based cuboid (hexahedron).
A pyramid.