**Core Concept**
The question requires knowledge of anticoagulants, specifically oral thrombin inhibitors. Thrombin inhibitors are a class of medications that prevent the conversion of fibrinogen to fibrin, thereby inhibiting blood clot formation. Oral thrombin inhibitors are a subclass of direct thrombin inhibitors, which directly bind to thrombin, preventing its activity.

**Why the Correct Answer is Right**
Dabigatran is an oral direct thrombin inhibitor that works by directly binding to thrombin (Factor IIa) and inhibiting its activity. This prevents the conversion of fibrinogen to fibrin, thereby preventing blood clot formation. Dabigatran is a prodrug that is converted to its active form, dabigatran etexilate, in the body. It has a predictable pharmacokinetic profile and is used to prevent stroke and systemic embolism in patients with atrial fibrillation.

**Why Each Wrong Option is Incorrect**
**Option A:** Apixaban is an oral direct Factor Xa inhibitor, not a thrombin inhibitor. It works by inhibiting Factor Xa, which is involved in the coagulation cascade.
**Option B:** Rivaroxaban is also an oral direct Factor Xa inhibitor, similar to apixaban. It inhibits Factor Xa, preventing the conversion of prothrombin to thrombin.
**Option C:** Edoxaban is another oral direct Factor Xa inhibitor, which works similarly to apixaban and rivaroxaban.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that oral direct thrombin inhibitors (e.g., dabigatran) have a predictable pharmacokinetic profile and do not require routine monitoring, unlike warfarin or heparin. However, they still require regular monitoring of renal function due to their excretion.

**Correct Answer:** D. Dabigatran