## Core Concept
The question presents a chest X-ray (CXR) scenario, implying the need for further diagnostic investigation based on the findings. The next step in management would logically depend on the specific abnormalities observed on the CXR. However, without the image, we can infer that the question likely involves common indications for further imaging or diagnostic tests following a CXR.

## Why the Correct Answer is Right
Given that the correct answer is not specified, let's assume a common scenario: if the CXR shows signs suggestive of a specific condition such as pneumonia, interstitial lung disease, or a mass lesion, the next investigation could logically be a **Computed Tomography (CT) scan of the chest**. A CT scan provides more detailed images of the lung parenchyma, mediastinum, and surrounding structures compared to a CXR. It is particularly useful for characterizing lung lesions, assessing the extent of disease, and guiding further management.

## Why Each Wrong Option is Incorrect
- **Option A:** If this option represents an incorrect choice, without specifics, we can hypothesize it might be less sensitive or specific than a CT scan for detailed evaluation, such as an ultrasound, which is not typically the next step for evaluating lung parenchyma or mediastinal structures.
- **Option B:** Similarly, if this option is incorrect, it could represent an investigation that is not as directly relevant or as immediately necessary as a CT scan, such as a routine blood test or a different imaging modality not as directly suited for lung evaluation.
- **Option C:** This could potentially represent another imaging modality or test that, while useful in certain contexts, is not the immediate next step following a CXR that shows an abnormality requiring detailed evaluation.

## Clinical Pearl / High-Yield Fact
A key point to remember is that when a CXR shows an abnormality that requires further characterization, especially for conditions like lung nodules or masses, a **CT scan of the chest** is often the next best diagnostic step. This is because CT scans can provide detailed information that can help in planning the patient's management, including the need for biopsy or surgical intervention.

## Correct Answer: B. CT Chest.