**Core Concept**
DNA repair defects are a group of genetic disorders characterized by impaired ability to repair DNA damage, leading to accumulation of mutations and increased risk of cancer. The most well-known DNA repair defect is Xeroderma Pigmentosum (XP), which results from mutations in genes involved in nucleotide excision repair (NER).

**Why the Correct Answer is Right**
Nucleotide excision repair is a process that removes DNA damage caused by ultraviolet (UV) light and other mutagenic agents. The process involves the recognition of damaged DNA, unwinding of the DNA double helix, removal of the damaged nucleotides, and synthesis of new DNA to replace the removed section. In XP, mutations in genes such as XPA, XPC, and XPC lead to impaired NER, resulting in accumulation of mutations and increased risk of skin cancers. The defective DNA repair mechanism is responsible for the characteristic skin lesions and increased cancer risk in XP patients.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** This option is not provided.
* **Option C:** This option is not provided.
* **Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
XP patients are highly sensitive to UV light and have a significantly increased risk of skin cancers, making them a classic example of the relationship between DNA repair defects and cancer.

**Correct Answer:** D. Xeroderma Pigmentosum (XP)