Braddy connected the loose wire to the battery and created an electromagnet. He picked up 45 thumb tacks with his electromagnet, though his goal was to pick up 50 thumb tacks. What could Braddy do to increase the strength of his electromagnet and pick up more thumbtacks? A) Use fewer coils of wire. B) Use a screw instead of a nail. C) Use two batteries instead of one. D) Replace the nail with a piece of steel.