The correct answer is:
D) You can do any of the above.
Each of the methods described can help in making a magnetic material a permanent magnet:
- A) Leaving it in the magnetic field of an actual magnet can help align its magnetic domains, turning it into a permanent magnet.
- B) Heating the material while it is in a magnetic field can also align the domains as they become more mobile at higher temperatures, leading to permanent magnetization as it cools and retains that alignment.
- C) Heating and then cooling in a strong magnetic field can also align domains effectively, reinforcing permanent magnetization.
Thus, all of the methods can indeed contribute to creating a permanent magnet.