Okay, let's tackle this question. The patient has hemoptysis and a persistent cough, and the chest X-ray is normal. The next step is the investigation. Hmm, hemoptysis can be due to various causes like bronchiectasis, tuberculosis, or even lung cancer. But the chest X-ray is normal, so maybe the issue isn't visible on a standard X-ray. What's the next step here?

Well, if the chest X-ray is normal but symptoms persist, a CT scan would be the next logical step. CT is more sensitive and can detect smaller lesions, bronchiectasis, or other abnormalities that X-ray might miss. So, maybe the answer is CT of the chest. Let me check the options again. The user didn't list the actual options, but in typical cases, options might include sputum culture, bronchoscopy, CT, or maybe a different imaging modality.

Wait, the question is about the next best investigation. So after a normal chest X-ray, CT is indeed the next step. Bronchoscopy might be considered if there's a suspicion of a tumor or to get a biopsy, but CT would come first to look for structural issues. Sputum culture is for infection, but if the X-ray is normal, maybe the infection isn't the main issue. So the correct answer should be CT of the chest. Let me confirm the reasoning again. Yes, CT is the gold standard for evaluating hemoptysis when X-ray is normal. It can show bronchiectasis, nodules, or other lung abnormalities. The other options would be less effective in this scenario. So the correct answer is CT of the chest.

**Core Concept**
Hemoptysis with a normal chest X-ray necessitates a more sensitive imaging modality to detect occult pathology such as bronchiectasis, small nodules, or early-stage lung cancer. **CT (computed tomography)** of the chest is the gold standard for evaluating such cases due to its superior resolution compared to plain radiographs.

**Why the Correct Answer is Right**
**CT of the chest** provides detailed cross-sectional imaging of the lung parenchyma, bronchi, and vasculature. It can identify subtle abnormalities like bronchiectasis, interstitial lung disease, small pulmonary nodules, or vascular malformations (e.g., arteriovenous fistulas) that are invisible on chest X-ray. For hemoptysis, CT is particularly useful to detect **bronchiectasis** (common in chronic infections) or **pulmonary embolism** (less common but critical to exclude).

**Why Each Wrong Option is Incorrect**
**Option A:** Sputum culture is used for diagnosing infections (e.g., tuberculosis, bacterial pneumonia) but is not diagnostic for structural causes of hemoptysis.
**Option B:** Bronchoscopy is valuable for visualizing airway lesions or obtaining biopsies but is invasive and not first-line when imaging is normal.
**Option C:** MRI is not indicated for hemoptysis; it lacks the anatomical detail of CT for lung parenchyma and is less accessible in acute settings.

**Clinical Pearl / High-Yield Fact**
Never miss **CT of the chest** as the next step after a normal X-ray in hemoptysis. Remember the "CT rule" for hemoptysis: **CT >

✓ Correct Answer: B. High resolution CT