Which of the following was considered to be a clear sign of death in the past?

A. A flat EEG

B. Moderate brain stem function

C. Lack of higher cortical brain function

D. Rigor mortis

D. Rigor mortis

Explanation:

Rigor mortis is considered to be the third stage of death. It is the phenomenon when the body's muscles and bones becomes stiffen and rigid after few hours of death. This is because the muscles of the body contract after one is dead.

It lasts for about seventy hours after death.

It is one of the recognizable signs of death in the past where the postmortem muscles of the dead becomes stiff.

Hence the answer is - -

D. Rigor mortis