**Core Concept**
Pneumonia is a respiratory infection characterized by inflammation of the lung parenchyma, typically caused by bacterial, viral, or fungal pathogens. The clinical features of pneumonia are diverse and depend on the underlying cause, severity, and individual patient factors.

**Why the Correct Answer is Right**
The clinical presentation of pneumonia often includes symptoms such as cough, fever, chest pain, and shortness of breath. The presence of **pleuritic chest pain**, which worsens with deep breathing or coughing, is a characteristic feature of pneumonia. This pain is caused by inflammation of the pleura, the thin membrane surrounding the lungs. Additionally, patients with pneumonia may exhibit signs of systemic illness, such as fatigue, malaise, and anorexia. In severe cases, pneumonia can lead to **hypoxemia**, a condition characterized by low blood oxygen levels, which can compromise vital organs and require urgent medical attention.

**Why Each Wrong Option is Incorrect**
**Option A:** While cough is a common symptom of pneumonia, it is not the only clinical feature. Other symptoms, such as fever and pleuritic chest pain, are more specific to pneumonia.
**Option B:** Chest pain is a feature of pneumonia, but it is not the only cause of chest pain. Other conditions, such as myocardial infarction or musculoskeletal disorders, can also cause chest pain.
**Option C:** Shortness of breath is a feature of pneumonia, but it is not the most characteristic symptom. **Hypoxemia**, which can occur in severe pneumonia, is a more specific indicator of respiratory compromise.

**Clinical Pearl / High-Yield Fact**
The **CURB-65** score is a useful clinical tool for predicting mortality in patients with pneumonia. This score takes into account five factors: **C**onfusion, **U**remia, **R**espiratory rate, **B**lood pressure, and **65** years of age or older. A higher score is associated with increased mortality risk.

**Correct Answer:** A. Cough, fever, pleuritic chest pain, and shortness of breath are common clinical features of pneumonia.