Final answer:
The correct answer is d. -100 °C or below. Ultra-low temperature storage is necessary for preserving the viability of cryopreserved skin and other biological samples, capable of reaching temperatures lower than -70 °C and in some cases, down to -196 °C.
Step-by-step explanation:
The correct answer is d. -100 °C or below:
The storage of frozen or cryopreserved skin, as well as other biological samples like bacterial cultures and medical specimens, is commonly done at ultra-low temperatures to maintain their viability over long periods. Ultra-low temperatures in the context of cryopreservation are typically below -70 °C. These temperatures are essential because they significantly slow down biological and chemical processes, which could otherwise degrade the sample.
As per the provided reference, certain medical specimens are stored at -70 °C while some biological materials, like cells preserved in liquid nitrogen, are kept at temperatures as low as -196 °C. To achieve such low temperatures, specialized equipment such as ultra-low freezers or liquid nitrogen storage tanks are utilized.