Storing backup data off-site is the correct answer because it provides geographical diversity. In the event that there is a site-specific disaster, such as a fire or natural disaster, the chances of the backup data becoming compromised are reduced. On-site storage would put the backup data at the same risk as the original data, and cloud storage without specifying the need for distant geographic location does not guarantee the data is stored remotely. Personal devices are not recommended for professional backup purposes due to security and capacity concerns, and they do not inherently provide geographical diversity.