**Core Concept**
Vitamin-A deficiency leads to impaired epithelial cell differentiation and function, resulting in increased susceptibility to cancerous lesions. This is due to the critical role of retinoic acid, a derivative of Vitamin-A, in regulating cell growth, differentiation, and apoptosis.

**Why the Correct Answer is Right**
Retinoic acid exerts its effects by binding to retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which are transcription factors that regulate the expression of target genes involved in cell cycle control, apoptosis, and differentiation. In Vitamin-A deficiency, the lack of retinoic acid leads to uncontrolled cell growth, accumulation of mutations, and eventual development of cancerous lesions. The relationship between Vitamin-A deficiency and cancer is well-established, with Vitamin-A supplementation shown to reduce the incidence of certain cancers, such as cervical cancer.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Vitamin-A deficiency does not directly cause cancerous lesions through an immune-mediated response. While Vitamin-A is important for immune function, its deficiency primarily affects epithelial cell differentiation and function.

**Option B:** This option is incorrect because Vitamin-A deficiency does not directly cause cancerous lesions through a decrease in oxidative stress. While Vitamin-A has antioxidant properties, its deficiency primarily affects cell differentiation and function.

**Option C:** This option is incorrect because Vitamin-A deficiency does not directly cause cancerous lesions through an increase in DNA damage. While Vitamin-A is important for maintaining genomic stability, its deficiency primarily affects cell differentiation and function.

**Clinical Pearl / High-Yield Fact**
Vitamin-A deficiency is a significant public health concern, particularly in areas with limited access to nutrient-rich foods. Supplementing with Vitamin-A has been shown to reduce the incidence of certain cancers, making it an important component of cancer prevention strategies.

**Correct Answer: D. Impaired epithelial cell differentiation**