What is a common symptom of pneumonia?

A productive cough is a hallmark symptom of pneumonia, as it involves the expulsion of mucus or phlegm from the respiratory tract. This symptom arises due to the infection process, where the lungs become inflamed, and the body produces mucus in an attempt to trap and eliminate pathogens.

Individuals with pneumonia typically experience a cough that may be accompanied by discolored sputum, often indicating the presence of bacteria or other infectious agents. This symptom is crucial in diagnosing pneumonia as it reflects the body's response to the infection and assists healthcare providers in determining the severity and appropriate treatment.

The other options present symptoms that may be associated with different medical conditions but are not typically primary indicators of pneumonia. For instance, severe chest pain might occur in various respiratory issues but does not specifically point to pneumonia. Weight loss can indicate chronic conditions or prolonged illness but is not a direct symptom of pneumonia, and muscle weakness is often associated with a range of conditions including various infections or systemic illnesses, rather than being specific to pneumonia.