The 'rw' option is used to mount a filesystem with both read and write permissions. If a filesystem is unintentionally mounted as read-only, ensuring that the 'rw' option is set during the mount process will resolve the issue, allowing users to perform write operations once more. Other options, such as 'ro', 'sync', and 'user', have specific uses: 'ro' mounts the filesystem as read-only, 'sync' ensures that input/output operations are done synchronously, and 'user' allows an ordinary user to mount the filesystem without requiring superuser privileges. However, these do not address the problem described.