Final answer:
When embalming severely dehydrated remains, a practitioner should use a low-index arterial fluid, which helps to rehydrate tissues and preserve a more natural appearance.
Step-by-step explanation:
When embalming severely dehydrated remains, the practitioner should use b. A low-index arterial fluid. This is similar to how a dehydrated human patient is given fluids intravenously in a medical setting. For patients, an isotonic saline solution is used because it matches the body's own salinity and therefore does not cause further dehydration or overhydration of the cells. In the context of embalming, a high-index fluid would contain a higher concentration of preservative chemicals which could further dehydrate the tissues, potentially causing them to become more brittle and less natural in appearance. Conversely, a low-index fluid has a lower concentration of preservatives and can help to mildly rehydrate the body's tissues, allowing for a better preservation and more natural appearance.
In reference to ancient practices, severe desiccation was sought after during the mummification process, which is notably different from the contemporary goal of preserving a natural look in modern embalming practices.