Simple phenomena of magnetism — practice question

Which method would not demagnetise a bar magnet?

• AHeat the bar magnet and place it in the east-west direction to cool.
• BPlace the bar magnet in the east-west direction and hammer it.
• CPlace the bar magnet in a coil connected to an a.c. supply and slowly withdraw it.
• DPlace the bar magnet in a coil connected to a d.c. supply and slowly withdraw it.