**Core Concept**
Pulmonary embolism (PE) is a blockage of an artery in the lungs by a substance such as a blood clot. Accurate diagnosis is crucial due to its potential for high morbidity and mortality. The best method to diagnose PE involves a combination of clinical assessment, imaging, and laboratory tests.

**Why the Correct Answer is Right**
The most accurate and widely used method to diagnose PE is computed tomography pulmonary angiography (CTPA). This imaging technique provides detailed visualization of the pulmonary arteries and allows for the detection of clots. CTPA is particularly useful because it can also identify other potential causes of symptoms, such as pulmonary hypertension or tumors. Additionally, CTPA has high sensitivity and specificity for PE, making it a gold standard for diagnosis.

**Why Each Wrong Option is Incorrect**
**Option A:** D-dimer testing is often used as a screening tool for PE but is not specific or sensitive enough to be used as a standalone diagnostic method.
**Option B:** Ventilation-perfusion (V/Q) scan is an alternative imaging technique but is less accurate than CTPA and has higher false-negative rates.
**Option C:** Pulmonary angiography is a more invasive procedure that is typically reserved for cases where CTPA is inconclusive or not possible.

**Clinical Pearl / High-Yield Fact**
A high D-dimer level is not specific for PE and can be elevated in various conditions, such as recent surgery, trauma, or malignancy. Therefore, a positive D-dimer result should be followed by further diagnostic testing, such as CTPA.

**Correct Answer:** C. Pulmonary angiography is a more invasive procedure that is typically reserved for cases where CTPA is inconclusive or not possible.