A "Hypochondriac'' is a person who is excessively worried about their health, often fearing serious illness without medical evidence.
Step 1: Analyze options
- (A) Altruist: a person unselfishly concerned for others.
- (B) Extrovert: a person who is outgoing and sociable.
- (C) Hypochondriac: a person excessively concerned about health.
- (D) Skeptic: a person inclined to doubt accepted opinions.
Therefore, option (C) is the correct answer.