Which of the following must be retained at a constant temperature of less than 40°F for no more than 96 hours?

An un-embalmed body must be retained at a constant temperature of less than 40°F for no more than 96 hours to prevent decomposition and to maintain public health standards. This requirement is crucial because un-embalmed bodies are more susceptible to rapid decay due to the absence of chemical preservation that embalming provides. Keeping the body refrigerated helps to slow down the natural processes of decomposition by inhibiting bacterial growth and other changes that occur after death.

Embalmed bodies, on the other hand, can be preserved for longer periods and typically do not require such strict temperature controls. Cremated remains do not have the same biological concerns since they have already been processed through cremation, and buried bodies are subject to the environmental conditions of the burial site. Thus, the specific time and temperature regulation is applicable only to un-embalmed bodies in this context.