6. Krystal is exploring the properties of iron. She takes a large iron nail and finds that the nail does not attract other metal objects. Next, she uses a battery and copper wire to transform the nail into an electromagnet. When she connects the circuit, the nail becomes magnetic and can pick up small metal objects like paper clips. What best describes what has happened to the iron in the nail that causes it to become magnetic?

A. A physical change has occurred, because the chemical properties of the iron remain the same.

B. A physical change has occurred, because there is a chemical attraction between the iron and paper clips.

C. A chemical change has occurred, because there is a chemical attraction between the iron and paper clips.

D. A chemical change has occurred, because the chemical energy in the battery is transformed into magnetic energy in the iron.