Lung tuberculosis is caused by

Options

A. Pseudomonas aeruginosa
B. Mycobacterium tuberculosis
C. Streptococcus pneumoniae
D. Escherichia coli

Explanation

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks about the causative agent of lung tuberculosis. It provides four options: Pseudomonas aeruginosa, Mycobacterium tuberculosis, Streptococcus pneumoniae, and Escherichia coli.

2. **Identifying the Disease**: Lung tuberculosis is a contagious disease characterized by symptoms such as a persistent cough and mucus production. It primarily affects the lungs.

3. **Analyzing the Options**:
- **Option A: Pseudomonas aeruginosa**: This bacterium is known to cause lung pneumonia and infections, especially in hospital settings, but it does not cause lung tuberculosis. Therefore, this option is incorrect.
- **Option B: Mycobacterium tuberculosis**: This is the bacterium specifically known to cause lung tuberculosis. It is the correct answer.
- **Option C: Streptococcus pneumoniae**: This bacterium is primarily associated with pneumonia, not tuberculosis. Thus, this option is also incorrect.
- **Option D: Escherichia coli**: While some strains can cause gastrointestinal diseases, E. coli is not associated with lung tuberculosis. This option is incorrect as well.

4. **Conclusion**: After evaluating all the options, the correct answer to the question "Lung tuberculosis is caused by" is **Mycobacterium tuberculosis**.

### Final Answer:
**Mycobacterium tuberculosis**

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