**Core Concept**
Vitamin K plays a crucial role in the carboxylation of clotting factors in the liver, allowing them to bind calcium ions and adhere to phospholipid surfaces, which is essential for blood coagulation. The vitamin acts as a cofactor for the enzyme gamma-glutamyl carboxylase, enabling the conversion of glutamate residues to gamma-carboxyglutamate.

**Why the Correct Answer is Right**
Vitamin K-dependent clotting factors include prothrombin (factor II), factors VII, IX, and X. The carboxylation process is necessary for the activation of these factors, which then participate in the coagulation cascade. The gamma-glutamyl carboxylase enzyme requires Vitamin K as a cofactor to facilitate the conversion of glutamate to gamma-carboxyglutamate. This post-translational modification is essential for the proper function of these clotting factors.

**Why Each Wrong Option is Incorrect**
* **Option A:** Vitamin C is involved in collagen synthesis and iron absorption, but it is not directly related to the carboxylation of clotting factors.
* **Option B:** Vitamin D is essential for calcium homeostasis and bone health, but it does not play a role in clotting factor carboxylation.
* **Option C:** Vitamin B12 is necessary for DNA synthesis and the maintenance of the nervous system, but it is not involved in the carboxylation of clotting factors.

**Clinical Pearl / High-Yield Fact**
Warfarin, an anticoagulant medication, works by inhibiting the synthesis of Vitamin K-dependent clotting factors, leading to a decrease in the production of these essential proteins.

**Correct Answer:** C. Vitamin K.