Vitamin A in human nutrition plays a particularly important role in the healthy functioning of which body part?

Introduction / Context:
Vitamins are essential nutrients that support specific functions in the body. Vitamin A is well known for its relationship with vision, especially night vision. Many exam questions connect vitamin A with symptoms such as night blindness and dryness of the eyes. This question checks whether you link vitamin A correctly with eye function.

Given Data / Assumptions:

• Vitamin A is a fat soluble vitamin.
• Deficiency of vitamin A can cause night blindness and other eye problems.
• The options mention various body systems such as brain, hair and bones.

Concept / Approach:
Vitamin A, in the form of retinal, is part of the light sensitive pigment in the retina of the eye. This pigment is essential for vision in low light conditions. Vitamin A also helps maintain the health of the cornea and conjunctiva. Deficiency leads to night blindness, dryness and in severe cases damage to the cornea. While vitamin A has additional roles in immunity and cell growth, its strongest textbook association is with healthy vision.

Step-by-Step Solution:
Step 1: Recall that vitamin A deficiency commonly causes night blindness. Step 2: Connect night blindness and dryness of eyes directly with eye health. Step 3: Recognise that vitamin A is part of the visual cycle in the retina, helping in adaptation to dim light. Step 4: Compare this strong relationship with weaker or indirect roles in brain, hair or bone alone. Step 5: Choose the option that clearly states its important role in healthy eye vision and adaptation to dim light.

Verification / Alternative check:
Nutrition and biology textbooks describe how retinal, derived from vitamin A, combines with opsin proteins to form rhodopsin and other visual pigments. These pigments change configuration when they absorb light, starting nerve impulses that reach the brain. This mechanism explains why lack of vitamin A leads to poor adaptation to low light and night blindness. No such direct mechanism is described specifically for scalp hair or bone growth as the main function of vitamin A.

Why Other Options Are Wrong:
Option b mentions complex brain functions, which depend on many nutrients and are not uniquely tied to vitamin A.

Option c focuses only on hair growth, which is more directly affected by proteins and some B vitamins rather than vitamin A as a main factor.

Option d points to bone formation, which is more strongly linked with vitamin D and calcium, although vitamin A does have some influence on growth. It is not the primary association tested in basic nutrition questions.

Common Pitfalls:
Students sometimes mix up the functions of vitamins A and D because both are fat soluble and involved in growth. Another pitfall is to think that any vitamin must be equally important for all tissues, which is not true. Focusing on the classic deficiency disease for each vitamin helps fix their main roles in memory.

Final Answer:
Vitamin A plays a key role in healthy eye vision and adaptation to dim light.