Disease pneumonia is due to

Options

A. Virus
B. Bacterium
C. Cyanobacterium
D. Protozoan.

Answer

### Step-by-Step Solution:

1. **Understanding Pneumonia**:
- Pneumonia is an inflammatory condition of the lungs. It primarily affects the alveoli, which are the small air sacs where gas exchange occurs.

2. **Symptoms of Pneumonia**:
- The disease is characterized by symptoms such as a persistent cough (which can be productive or dry), chest pain, fever, difficulty breathing, and shortness of breath.

3. **Causative Agents of Pneumonia**:
- Pneumonia can be caused by various pathogens, including bacteria and viruses.
- The most common bacterial cause of pneumonia is *Streptococcus pneumoniae*.

4. **Role of Viruses**:
- While bacteria are the most common cause, viruses can also lead to pneumonia. Respiratory viruses, including influenza and coronaviruses, can cause pneumonia.

5. **Evaluating the Options**:
- **Virus**: While viruses can cause pneumonia, they are not the most common cause.
- **Bacterium**: This is the most common cause of pneumonia, making it the best answer.
- **Cyanobacterium**: These are blue-green algae and do not cause pneumonia.
- **Protozoan**: Protozoa are not associated with pneumonia but with other diseases.

6. **Conclusion**:
- Based on the information, the correct answer to the question "Disease pneumonia is due to" is **Bacterium**.

### Final Answer:
- **Pneumonia is primarily caused by a bacterium, specifically *Streptococcus pneumoniae*.**

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