**Core Concept**
Pulmonary embolism (PE) is a life-threatening condition caused by a blockage in one of the pulmonary arteries, typically due to a dislodged blood clot (thrombus) originating from the deep veins of the legs or other parts of the body. The blockage can lead to impaired gas exchange, acute right heart strain, and potentially fatal outcomes if not promptly treated.

**Why the Correct Answer is Right**
The correct answer refers to the consequences of pulmonary embolism. In the context of PE, the following effects are commonly observed:
- **Hypoxemia**: Reduced oxygen levels in the blood due to impaired gas exchange in the lungs.
- **Tachypnea**: Rapid breathing rate as the body attempts to compensate for inadequate oxygenation.
- **Acute right heart strain**: The right ventricle of the heart may become overwhelmed, leading to potential failure.

**Why Each Wrong Option is Incorrect**
**Option A:** Not applicable (missing option)
**Option B:** Not applicable (missing option)
**Option C:** Not applicable (missing option)
**Option D:** Not applicable (missing option)

**Clinical Pearl / High-Yield Fact**
A key clinical correlation is that patients with PE often present with **unilateral leg swelling**, which can be a subtle yet critical clue for diagnosing this life-threatening condition.

**Correct Answer:** Not provided (please provide the options for accurate explanation)