The Muscles of a Recently Deceased Human Can Remain in a Contracted

The muscles of a recently deceased human can remain in a contracted state, termed rigor mortis, for several hours. What prevents the muscles from relaxing soon after death?

A) the depletion of ATP required to break actin-myosin bonds
B) calcium ions cannot bind to the troponin complex
C) myoglobin is overwhelmed by a buildup of carbon dioxide
D) sodium ions required for action potentials are concentrated outside the muscle cells