Answer:
D 10cm
Explanation:
As the distance between the two objects(magnet and Ferromagnetic Metals and Alloys) increases the magnetic for will decrease
if a iron nail is kept 1cm far from a magnet then the magnet will atract it easily but if the same iron nail is kep 3cm far from the magnet then the magnet won't attract it easily .
(Ferromagnetic materials such as iron, nickel and cobalt are attracted to magnets, as well as rare-earth metals like gadolinium, neodymium and samarium.)
Hope you've understood
