Record evidence for interactions between tectonic plates.
As you explore the lesson, gather
evidence to help explain landforms
and geological processes that occur
along plate boundaries and the
processes that drive plate motion.

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.

i think its d if wrong im sorry