A steel bar is set out along the East-West line so that it can be demagnetised. There is no magnet close by. Which method is unsuitable?
- AHammering the bar.
- BHeating the bar to a very high temperature.
- CSlowly taking the bar out of a coil that carries an alternating current.
- DSlowly taking the bar out of a coil that carries a direct current.