what are the four stages of rigor mortis?
['Absent. In this stage, the body is still receiving small bits of oxygen anaerobically. ... ', "Minimal. The body's muscles have just begun to stiffen up. ... ", 'Moderate. More muscles are beginning to stiffen and it has become obvious that the body is no longer loose or flexible.', 'Advanced. ... ', 'Complete. ... ', 'Passed.']