**Core Concept**
The post-translation carboxylation of clotting factors is a critical process that enables the proper functioning of these proteins in the coagulation cascade. This process involves the conversion of glutamic acid residues to gamma-carboxyglutamic acid, which is essential for the binding of calcium ions and the subsequent activation of clotting factors.

**Why the Correct Answer is Right**
The correct answer is Vitamin K. Vitamin K-dependent carboxylase is a specific enzyme that catalyzes the post-translation carboxylation of glutamic acid residues in clotting factors II, VII, IX, and X. This process requires the presence of Vitamin K, which serves as a cofactor for the enzyme. The Vitamin K-dependent carboxylase enzyme introduces a carboxyl group (-COOH) onto the glutamic acid residues, resulting in the formation of gamma-carboxyglutamic acid. This modification enables the clotting factors to bind to phospholipid surfaces and interact with other coagulation proteins.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Vitamin K is essential for the carboxylation of clotting factors, but it is not the enzyme responsible for this process.
**Option B:** This option is incorrect because Vitamin D is a related compound, but it is not involved in the carboxylation of clotting factors.
**Option C:** This option is incorrect because there is no evidence to suggest that a specific "carboxylase" enzyme is required for this process. Vitamin K-dependent carboxylase is the correct term.

**Clinical Pearl / High-Yield Fact**
Vitamin K-dependent carboxylation is a critical process that can be impaired by certain medications, such as warfarin, which inhibits the activity of Vitamin K-dependent carboxylase. This can lead to bleeding disorders and increased risk of thromboembolic events.

**Correct Answer:** D. Vitamin K.