**Core Concept**
Pulmonary embolism (PE) is a blockage of an artery in the lungs by a blood clot. Diagnosing PE involves clinical evaluation, imaging studies, and laboratory tests. This question requires knowledge of tests that can help exclude PE.

**Why the Correct Answer is Right**
The correct answer will be a test that does not have a high negative predictive value (NPV) for pulmonary embolism. This means that even if the test result is negative, it does not rule out PE with a high degree of certainty. The D-dimer test is a fibrin degradation product that increases in response to clot formation. However, it is not specific to PE and can be elevated in many conditions, including cancer, infections, and inflammation.

**Why Each Wrong Option is Incorrect**
**Option A:** D-dimer test is not a definitive test for PE, but a negative result can help exclude it in patients with low pre-test probability. However, a positive result does not confirm PE.
**Option B:** A normal chest X-ray does not exclude PE, as the clot may not be visible on X-ray.
**Option C:** A normal ECG does not exclude PE, as the ECG may not show signs of PE even if it is present.

**Clinical Pearl / High-Yield Fact**
A negative D-dimer test can help exclude PE in patients with low to moderate pre-test probability, but it is not a substitute for clinical evaluation and imaging studies.

**Correct Answer:** D. D-dimer test