You have a steel bar that you want to turn into an electromagnet. So, you wrap some insulated cord around the bar, and pass current through the cord. Which of these currents will give you an electromagnet that is useful, in practical terms? A. DC current with a supply and return path through the cord B. AC current C. DC current D. AC current with a supply and return path through the cord (so like a standard electric power cord) E. All of these options will give you a practical electromagnet