Not every AB5 molecule has a square pyramid structure. While some AB5 molecules, such as phosphorus pentachloride (PCl5), do have a square pyramid structure, others may have different structures depending on the atom involved and its geometry. For example, SF5Cl has a trigonal bipyramidal structure, not a square pyramid. The actual structure depends on the specific molecular geometry and the arrangement of atoms and lone pairs around the central atom.
So, the correct option is (C): Every AB5 molecule does in fact have square pyramid structure