A metal bar is put inside a current-carrying coil, as shown in diagram 1. A small current flows in the coil. The bar is able to support several nails, as shown in diagram 2. When the current in the coil is switched off, the nails fall away. Which row is correct?
- Asoft iron; it makes no difference
- Bsoft iron; the bar holds more nails
- Csteel; it makes no difference
- Dsteel; the bar holds more nails