Final answer:
The dermatome is correctly set to a depth of 0.012 to 0.020 inches to harvest donor skin, which allows for a suitable layer of the epidermis and potentially a small portion of the upper dermis to be collected for grafting purposes.
Step-by-step explanation:
When retrieving donor skin, the dermatome, which is a medical instrument used to remove a portion of the epidermis, is set to a specific depth to ensure that only the right amount of skin is harvested. The correct depth is generally within a certain range to balance the need for viable graft tissue and the safety of the donor site. According to the options provided, the most commonly used depth setting for a dermatome when retrieving donor skin is 0.012 to 0.020 inches.
This range is sufficient to harvest a thin layer that includes part of the epidermis and possibly a small amount of the upper dermis, depending on the location and thickness of the individual's skin, as the epidermis varies in thickness across different parts of the body.