Which process involves the use of heat and flame to reduce remains to bone fragments or ashes?

The correct choice is cremation, which refers specifically to the process of using heat and flame to reduce human remains to bone fragments or ashes. This process typically occurs in a crematory, which is the facility designed for this purpose. During cremation, the remains are exposed to high temperatures, often exceeding 1400 degrees Fahrenheit, which effectively incinerates organic material, leaving behind primarily bone fragments.

While the term "crematory" refers to the physical location where cremation takes place, and "processing" refers to the methods used to handle the remains following the actual cremation, these terms do not accurately describe the act of applying heat and flame itself. "Pulverization" may be a part of the process that follows cremation if the remains are reduced further into ashes or fine particles, but it is not the primary process that involves heat and flame. Thus, the term cremation is the most precise and correctly identifies the process being asked about in the question.