**Core Concept**
Factor V Leiden is a genetic disorder caused by a mutation in the F5 gene, leading to a hypercoagulable state due to resistance to activated protein C (APC). This defect results in the formation of thrombin, which in turn contributes to the development of venous thromboembolism.

**Why the Correct Answer is Right**
The mutation in the F5 gene leads to a substitution of arginine to glutamine at position 506 (R506Q) in the factor V protein. This change renders the factor V protein resistant to inactivation by APC, resulting in an increased risk of thrombin formation and subsequent clotting. This mechanism is crucial in understanding the pathophysiology of factor V Leiden.

**Why Each Wrong Option is Incorrect**
**Option A:** This option might be incorrect as it might refer to another condition. However, without more information, it's hard to determine.
**Option B:** This option might be incorrect as it might refer to another condition. However, without more information, it's hard to determine.
**Option C:** This option might be incorrect as it might refer to another condition. However, without more information, it's hard to determine.

**Clinical Pearl / High-Yield Fact**
Factor V Leiden is the most common inherited cause of venous thromboembolism and is responsible for approximately 20-30% of cases in Caucasian populations.

**Correct Answer: C. Factor V Leiden.**