**Core Concept**
The investigation in question is related to diagnosing **pulmonary embolism (PE)**, a condition where one or more arteries in the lungs become blocked by a blood clot. The **rule out test** is crucial for quickly determining whether a patient has a PE, especially in emergency settings.

**Why the Correct Answer is Right**
Although the specific correct answer choice is missing, typically, the **D-dimer test** is considered a "rule out" test for pulmonary embolism because it has high sensitivity but low specificity. A negative D-dimer can effectively rule out PE in low-risk patients, due to its high negative predictive value.

**Why Each Wrong Option is Incorrect**
**Option A:** Without the specific choices, we cannot directly address each option. However, any option that is not a D-dimer test or another highly sensitive test for PE would be incorrect for a "rule out" scenario.
**Option B:** Similarly, without specifics, we cannot comment directly, but tests with low sensitivity or those not designed for rapid ruling out of PE would be incorrect.
**Option C:** This option would be incorrect if it represents a test with low sensitivity for PE or one that is not typically used in the acute setting for ruling out PE.
**Option D:** If this is not the D-dimer test or a comparable sensitive test, it would be incorrect for the purpose of a "rule out" test in massive pulmonary embolism.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that while the D-dimer test is useful for ruling out PE due to its high sensitivity, it has low specificity and thus cannot be used to confirm the diagnosis. Confirmatory tests like **CT pulmonary angiography (CTPA)** are needed for patients with a high suspicion of PE and a positive D-dimer.

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