**Core Concept**
Vitamin A is an essential nutrient that plays a crucial role in maintaining vision, immune function, and epithelial integrity. A deficiency in vitamin A can lead to various clinical manifestations, primarily affecting the eyes, skin, and mucous membranes.

**Why the Correct Answer is Right**
Vitamin A deficiency impairs the production of rhodopsin, a protein in the retina responsible for night vision. This leads to night blindness, a common symptom of vitamin A deficiency. The deficiency also affects the integrity of the epithelial cells, increasing the risk of infections and skin problems. Furthermore, vitamin A is essential for the proper functioning of the immune system, and a deficiency can lead to impaired immune responses.

**Why Each Wrong Option is Incorrect**
**Option A:** Night blindness is a well-documented consequence of vitamin A deficiency. It occurs due to impaired rhodopsin production in the retina.
**Option B:** Dry skin and mucous membranes are common manifestations of vitamin A deficiency, which can lead to increased susceptibility to infections.
**Option C:** Vitamin A deficiency can cause xerophthalmia, a condition characterized by dry eyes and impaired vision.

**Clinical Pearl / High-Yield Fact**
Remember that vitamin A deficiency can lead to night blindness, dry skin, and impaired immune responses. These symptoms can occur in combination, making vitamin A deficiency a significant public health concern in areas with limited access to this essential nutrient.

**Correct Answer: D.**