Human nutrition: Identify the vitamin deficiency that causes night blindness. Full question: Night blindness (poor vision in dim light) is caused by a deficiency of which vitamin? Choose the correct option.

Difficulty: Easy

Vitamin A (retinol)
Vitamin B₂ (riboflavin)
Vitamin C (ascorbic acid)
Vitamin D (calciferol)
Vitamin K (phylloquinone)

Correct Answer: Vitamin A (retinol)

Explanation:

Concept
Night blindness results from inadequate vitamin A, needed to form retinal (11-cis-retinal) for the visual pigment rhodopsin in rod cells.

Mechanism
Low vitamin A → impaired rhodopsin regeneration → poor scotopic (low-light) vision.

Final Answer
Vitamin A (retinol).

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