2. Which best represents a physical property of a substance?
A. Acids act as a corrosive to metal.
B. Gold has a density of 19.3 g/cm3.
C. Sodium combines with chlorine to create
sodium chloride.
D. Hydrochloric acid reacts with zinc metal,
creating hydrogen gas.

conduction, convection, radiation

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.