**Core Concept**
The question is testing the knowledge of a specific inherited thrombotic disorder, which is a condition characterized by an increased tendency to form blood clots due to a genetic mutation. This condition is caused by a defect in the coagulation pathway, leading to an imbalance in the delicate process of blood clotting.

**Why the Correct Answer is Right**
The correct answer is Factor V Leiden mutation, which is a point mutation in the F5 gene that codes for the coagulation factor V. This mutation leads to the activation of factor V, resulting in the formation of thrombin and subsequent clot formation. The Factor V Leiden mutation is a common inherited cause of thrombophilia, which is a condition characterized by an increased tendency to form blood clots.

**Why Each Wrong Option is Incorrect**
**Option A:** Antithrombin deficiency is another inherited thrombotic disorder, but it is less common than Factor V Leiden mutation.
**Option B:** Protein C deficiency is another rare inherited thrombotic disorder, but it is not the most common one.
**Option C:** Prothrombin gene mutation (G20210A) is a rare inherited thrombotic disorder, but it is not as common as Factor V Leiden mutation.

**Clinical Pearl / High-Yield Fact**
Factor V Leiden mutation is the most common inherited thrombotic disorder, affecting approximately 5% of the Caucasian population. It is a significant risk factor for deep vein thrombosis and pulmonary embolism.

**Correct Answer: D. Factor V Leiden mutation.**