Which of the following describes rigor mortis?

Rigor mortis refers to the post-mortem physiological process that leads to the stiffness of the body. It typically begins a few hours after death, as chemical changes in the muscles cause them to stiffen due to the depletion of ATP, which is necessary for muscle relaxation. This rigidity usually starts in the smaller muscle groups and then progresses to larger muscle groups over several hours. Eventually, it will diminish as decomposition progresses.

The other options describe different states or processes related to a body after death. For instance, a state of limpness pertains to the condition of a body immediately after death, where the muscles are relaxed—this is not what rigor mortis signifies. Skin changes, such as lividity or paleness, and decomposed appearances refer to the changes that occur over time following death, but these are separate phenomena from the stiffness associated with rigor mortis.