How should the fragment below BEST be revised?
Sleeping on its side, the mule twitching as it dreamed.
The mule, sleeping on its side, twitching. As it dreamed.
Sleeping on its side, the mule twitched as it dreamed.
Sleeping on its side. The mule twitched as it dreamed.
The mule was sleeping on its side, it twitched as it dreamed.