Which combining form is used as a prefix to indicate relationship to skin?

• A. sial/o
• B. gastr/o
• C. dermat/o
• D. aut/o

Answer: (C)

Dermat/o is the combining form that denotes skin. When it appears at the beginning of a term, it signals a relationship to the skin, as seen in words like dermatitis or dermatology. The other options refer to saliva (sial/o), the stomach (gastr/o), or self (aut/o), not skin. So the combining form that indicates a relationship to skin is dermat/o.