Which set of diseases are caused by bacteria?

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Accepted Answer

Step-by-step reasoning:

- Option (1): Influenza — caused by a virus (Orthomyxoviridae). Dengue — caused by a virus (Flavivirus). Cholera — caused by bacteria (Vibrio cholerae). Mixed causes → not all bacterial.
- Option (2): Typhoid — caused by bacteria (Salmonella typhi). Cholera — caused by bacteria (Vibrio cholerae). Tuberculosis — caused by bacteria (Mycobacterium tuberculosis). All three are bacterial diseases, so this set is entirely bacterial.
- Option (3): Dengue — viral; Malaria — protozoan (Plasmodium); Cholera — bacterial. Mixed causes → not all bacterial.
- Option (4): Malaria — protozoan; Common cold — viral (e.g., rhinoviruses); Influenza — viral. None are bacterial.

In set notation: $S_2=\{	ext{Typhoid},\ 	ext{Cholera},\ 	ext{Tuberculosis}\}$ and $S_2\subseteq	ext{Bacterial diseases}$, so option (2) is correct.

FINAL_ANSWER: b

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