To solve the question regarding which set of diseases belongs to the same category of causative agents, we will analyze each option provided.
### Step-by-Step Solution:
1. **Identify the Diseases and Their Causative Agents:**
- **Option 1:** Tetanus, Typhoid, Pneumonia
- Tetanus: Caused by the bacterium *Clostridium tetani*.
- Typhoid: Caused by the bacterium *Salmonella typhi*.
- Pneumonia: Can be caused by various bacteria, including *Streptococcus pneumoniae*.
- **Conclusion:** All three diseases are caused by bacteria.
2. **Analyze the Second Option:**
- **Option 2:** Dengue, Typhoid, Malaria
- Dengue: Caused by the dengue virus (a virus).
- Typhoid: Caused by the bacterium *Salmonella typhi* (a bacterium).
- Malaria: Caused by the protozoan *Plasmodium* (a protozoa).
- **Conclusion:** This option includes diseases caused by a virus, a bacterium, and a protozoan, so they do not belong to the same category.
3. **Analyze the Third Option:**
- **Option 3:** Chikungunya, Dengue, Malaria
- Chikungunya: Caused by the chikungunya virus (a virus).
- Dengue: Caused by the dengue virus (a virus).
- Malaria: Caused by the protozoan *Plasmodium* (a protozoa).
- **Conclusion:** This option includes two viral diseases and one protozoan disease, so they do not belong to the same category.
4. **Analyze the Fourth Option:**
- **Option 4:** Mumps, Polio, Plague
- Mumps: Caused by the mumps virus (a virus).
- Polio: Caused by the poliovirus (a virus).
- Plague: Caused by the bacterium *Yersinia pestis* (a bacterium).
- **Conclusion:** This option includes two viral diseases and one bacterial disease, so they do not belong to the same category.
5. **Final Conclusion:**
- After analyzing all options, the only set of diseases that belong to the same category of causative agents is **Option 1: Tetanus, Typhoid, and Pneumonia**, as all are caused by bacteria.
### Final Answer:
**The correct answer is: Tetanus, Typhoid, and Pneumonia.**
