Classification – Odd one out (vitamin-deficiency diseases vs infectious disease): Identify the outlier: Scurvy, Rickets, Night-blindness, Influenza.

Introduction / Context:
This item tests medical classification. Three options are classic vitamin-deficiency disorders; one is an infectious viral illness. Distinguishing etiology (cause) cleanly separates the outlier.

Given Data / Assumptions:

• Scurvy → deficiency of vitamin C.
• Rickets → deficiency of vitamin D (often with calcium/phosphate imbalance) in children.
• Night-blindness → commonly due to vitamin A deficiency.
• Influenza → acute respiratory infection caused by influenza viruses.

Concept / Approach:
Group by cause: nutritional deficiency vs infection. The single infectious condition is the odd one out.

Step-by-Step Solution:
Tag scurvy, rickets, night-blindness as deficiency diseases.Tag influenza as infectious, not deficiency-based.Select influenza as the unique member by etiology.

Verification / Alternative check:
Symptoms vary across these conditions, but etiology remains the decisive discriminator: only influenza is communicable and caused by a pathogen.

Why Other Options Are Wrong:

• Scurvy, Rickets, Night-blindness are nutrient-deficiency conditions rather than infections.

Common Pitfalls:
Confusing effects of deficiency (e.g., bone deformities in rickets) with infectious symptoms; focus on the underlying cause.

Final Answer:
Influenza