Final answer:
Microdermabrasion exfoliates the stratum corneum, which is the outermost layer of the epidermis, consisting of dead, keratinized cells that provide protection for the skin.
Step-by-step explanation:
The layer of the skin that microdermabrasion exfoliates is the stratum corneum. This is the most superficial layer of the epidermis and is exposed to the external environment.
It consists of 15 to 30 layers of dead, keratinized cells that provide protection against microbes, dehydration, and mechanical abrasion. Microdermabrasion aims to remove some of these dry, upper layers to keep the skin looking fresh and healthy. In the case of the student's question, the correct answer is c) stratum corneum.