A student wraps copper wire around an iron nail. Then she connects the ends of the wire to a battery, making an electromagnet. She notices that if she wraps more coils of wire around the bolt, then her electromagnet can pick up more paper clips. What conclusion can she draw?
A More coils of wire increases the density of the copper wire
B More coils of wire increases the length of the nail
C More coils of wire increases the strength of the electromagnet
D More coils of wire increases the mass of the battery