Rub the needle with one pole of the magnet repeatedly in one direction, pass the needle through the cork, and then float the cork in water.

The correct sequence is to first magnetize the needle, then assemble the compass, and finally float it.

1. Magnetize the needle: Rub the needle with one pole of the magnet, always in the same direction, lifting the magnet at the end of each stroke. This turns the iron needle into a magnet.
2. Assemble the compass: Pass the now-magnetized needle through the piece of cork.
3. Float the device: Place the cork with the needle in a bowl of water. The needle will now be free to rotate and will align itself in the North-South direction.

• Option A is impractical and ineffective.
• Option C misses the crucial magnetization step; an unmagnetized needle will not align itself.
• Option D describes an incorrect magnetization method; rubbing back and forth will not magnetize the needle effectively.

Ok