**Core Concept**
The question tests the understanding of the pathophysiology of pulmonary embolism, specifically the mechanism leading to sudden death and right-sided heart failure. The underlying principle is the relationship between the size of the pulmonary embolism and the resulting hemodynamic compromise.

**Why the Correct Answer is Right**
When a pulmonary embolism occurs, it obstructs blood flow through the pulmonary arteries, leading to an increase in pulmonary artery pressure and resistance. This increase in pressure and resistance causes the right ventricle to work against a higher afterload, leading to an increase in right ventricular pressure and eventually, right ventricular failure. A massive pulmonary embolism that obstructs 60% or more of the pulmonary artery is likely to cause a significant increase in pulmonary artery pressure and resistance, leading to sudden death and right-sided heart failure.

**Option A:** A small pulmonary embolism may cause some degree of obstruction, but it is unlikely to cause significant hemodynamic compromise, leading to sudden death and right-sided heart failure. This option is incorrect because the embolism is not large enough to cause significant obstruction.

**Option B:** While a massive pulmonary embolism is indeed likely to cause significant hemodynamic compromise, the correct answer requires a more specific criterion, which is the obstruction of 60% or more of the pulmonary artery. This option is incorrect because it does not specify the exact percentage of obstruction.

**Option D:** End artery obliteration refers to the blockage of a terminal branch of a vessel, which is not relevant to the pathophysiology of pulmonary embolism. This option is incorrect because it refers to a different type of vascular obstruction.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the size of the pulmonary embolism, not just its presence, determines the severity of hemodynamic compromise. The exact percentage of pulmonary artery obstruction required to cause significant compromise is 60% or more.

✓ Correct Answer: C. 60% or more of pulmonary artery is obstructed with emboli.