Select an option which is different from the rest in a certain way.

Correct option is C

Fever: A symptom (elevated body temperature) that can be caused by various conditions.
Fatigue: A general symptom of tiredness or exhaustion, often associated with various illnesses.
Flu: A specific illness caused by the influenza virus.
Pain: A general symptom that can result from various causes.
Analysis:
The difference lies in the nature of Flu compared to the other options:
Fever, Fatigue, and Pain are all general symptoms that can occur due to a wide range of causes.
Flu, however, is a specific illness and not just a symptom.
Conclusion: The correct answer is indeed: Ans. (c) Flu