What does "Derm/o" refer to?

The term "Derm/o" is a combining form that specifically refers to skin. It is derived from the Greek word "derma," which means skin. This prefix is commonly used in medical terminology to describe various conditions, procedures, or aspects related to the skin. For example, terms like dermatology (the study of the skin) and dermatitis (inflammation of the skin) utilize this prefix to denote their focus on skin health and diseases.

The other options relate to their own respective body systems or organs, but none have a connection to the skin like "Derm/o" does. Thus, the correct answer underscores the specific anatomical focus that "Derm/o" represents in medical terminology.