What is the difference between a mineral, a crystal and a gem?

Minerals occur naturally in the earth's crust and are defined as inorganic solids that have characteristic chemical composition and crystalline structures. ... A gemstone or gem is a piece of mineral crystal, which, in cut and polished form, is used to make jewelry or other adornments.

Explanation:

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.