Which command, with options, could be used to change an ext2 file system on /dev/hda1 to an ext3 file system?

Which command, with options, could be used to change an ext2 file system on /dev/hda1 to an ext3
file system?

Answer: tune2fs -j

Explanation:
/dev/hda1

From the man pages:
tune2fs – adjust tunable filesystem parameters on ext2/ext3/ext4 filesystems
-j Add an ext3 journal to the filesystem. If the -J option is not specified, the default journal
parameters will be used to create an appropriately sized journal (given the size of the filesystem)
stored within the filesystem.

Note that you must be using a kernel which has ext3 support in order to actually make use of the
journal.