The atom in the diagram has a neutral charge how many protons does it have

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

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.