The correct option is C They always exist in pairs.
The magnetic poles always exist in pairs. It is not possible to separate the two poles of a magnet. If a bar magnet is broken into two parts, each part is found to be a magnet. Each part has the property to attract small iron pieces. If these pieces are broken again and again, each part will still be a complete magnet having both the poles. Thus, the two poles of a magnet exist simultaneously and they can never be separated.