Answer:
The correct answer is option C, It was struck repeatedly, which caused the domains to randomize and the nail to become nonmagnetic.
Explanation:
A nail is made of either steel, iron, cobalt etc, (any other magnetic material). The specific characteristics of these metals is that they are ferromagnetic which means each of their atom will behave as tiny magnets. Thus a metal is first heated and then beaten by hammer so that their tiny polar domains get scattered and they cancel out magnetic effect of each other thereby making demagnetizing a magnetic nail.