The cork must also have been magnetized. The magnetic field of Earth affected the needle. The magnetic current in the bowl of water affected the needle. The teacher must have placed the magnet to the south of the bowl.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Alisha's teacher glued a needle to a piece of cork so that the needle would float. Then he used a magnet to magnetize the needle. When the needle was placed in a bowl of water, it turned to point north. Which best describes the reason that the needle pointed north?
Possibilities:
- The cork must also have been magnetized.
- The magnetic field of Earth affected the needle.
- The magnetic current in the bowl of water affected the needle.
- The teacher must have placed the magnet to the south of the bowl.

The magnetic field of Earth affected the needle.