The magnetic field lines prefer to pass through iron tnanaii why ?

The magnetic lines of force prefer to pass through iron than air. Explain why?

Why do magnetic lines prefer to pass through ferromagnetic substances (e.g. Fe) than through oil?

Why do magnetic lines of force prefer to pass through ferromagnetic materials?

Free electron always keep on moving in a conductor. Even then, no magnetic force acts on them in a magnetic field unless a current is passed through it. Why?

Magnetic lines of force prefer to pass through ferromagnetic substances than air,because permeability for ferromagnetic substances is