Demagnetization of magnets can be done by

Explanation

Demagnetisation of a magnet can occur through various methods that disrupt the alignment of its magnetic domains. Rough handling can physically jar the magnetic domains out of alignment. Heating increases atomic vibrations, which disrupts the orderly alignment of magnetic domains. Magnetising in the opposite direction directly counteracts the existing magnetic alignment. Therefore, all the provided methods can lead to demagnetisation, making Option D: All of the above the correct answer. Each of the other options only represents one aspect of demagnetisation, but all are valid methods.