**Core Concept**
The formation of hydroxyproline and hydroxylysine is a crucial step in the post-translational modification of collagen, a key protein component of the extracellular matrix. This process involves the hydroxylation of proline and lysine residues, which is essential for the stabilization and cross-linking of collagen fibers.

**Why the Correct Answer is Right**
The correct answer involves the enzyme prolyl hydroxylase and lysyl hydroxylase, which are responsible for catalyzing the hydroxylation of proline and lysine residues, respectively. This process requires the presence of vitamin C (ascorbic acid) as a cofactor, as it helps to maintain the iron in the active site of the enzymes in a reduced state, thereby facilitating the hydroxylation reaction. The absence of vitamin C leads to a deficiency in collagen synthesis, resulting in scurvy.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not mention the specific enzymes responsible for hydroxylation.
**Option B:** This option is incorrect because it does not specify the role of vitamin C in the hydroxylation reaction.
**Option C:** This option is incorrect because it does not provide any relevant information regarding the enzymes or cofactors involved in hydroxylation.

**Clinical Pearl / High-Yield Fact**
Vitamin C deficiency can lead to scurvy, a condition characterized by impaired collagen synthesis, leading to symptoms such as fatigue, malaise, and joint pain.

**Correct Answer: D. Vitamin C. Ascorbic acid.**