**Core Concept**
Pulmonary embolism is a significant concern in patients undergoing major orthopedic surgeries, such as Total Hip Replacement (THR). This is due to the increased risk of venous thromboembolism (VTE) in the postoperative period.

**Why the Correct Answer is Right**
The most common cause of death after Total Hip Replacement is pulmonary embolism. This is because the surgery triggers a hypercoagulable state, increasing the risk of deep vein thrombosis (DVT), which can then lead to a pulmonary embolism if a clot breaks loose and travels to the lungs. The risk is further exacerbated by factors such as prolonged immobility, obesity, and smoking.

**Why Each Wrong Option is Incorrect**
* **Option A:** While myocardial infarction is a significant concern in the postoperative period, it is not the most common cause of death after Total Hip Replacement.
* **Option B:** Stroke is a possible complication of surgery, but it is not the leading cause of mortality in this context.
* **Option C:** Sepsis is a serious infection that can occur after surgery, but it is not the most common cause of death after Total Hip Replacement.

**Clinical Pearl / High-Yield Fact**
To minimize the risk of pulmonary embolism after Total Hip Replacement, patients should be encouraged to mobilize as soon as possible, and pharmacological prophylaxis with anticoagulants or antiplatelet agents may be considered.

**Correct Answer:** C.