To determine the causative agent of the disease in primates with symptoms of nasal congestion, sore throat, and fever, we need to analyze the possible pathogens listed.
### Step-by-Step Solution:
1. **Identify Symptoms**: The symptoms presented are nasal congestion, sore throat, and fever. These are common symptoms associated with respiratory infections.
2. **Evaluate the First Line of Action**: The scientists injected an extract from blue-green mold (which is a type of fungus) as a treatment. However, the symptoms did not subside, indicating that the pathogen is likely not a fungus, as the treatment did not have any effect.
3. **Consider the Possible Pathogens**:
- **i. Virus**: Viruses are known to cause respiratory infections, such as the common cold, which can lead to nasal congestion, sore throat, and fever. Since the blue-green mold (fungus) did not alleviate the symptoms, this suggests that a viral infection could be the cause.
- **ii. Fungus**: As mentioned, the blue-green mold was ineffective, indicating that a fungal infection is unlikely to be the causative agent of these symptoms.
- **iii. Conjugation Deficient Bacterium**: Certain bacteria can cause respiratory symptoms, such as Streptococcus pneumoniae, which can lead to sore throat and fever. However, the blue-green mold would not be effective against bacterial infections.
- **iv. Tapeworm**: Tapeworms are parasitic worms that typically cause gastrointestinal issues, not respiratory symptoms, making them an unlikely cause of the symptoms described.
4. **Conclusion**: Based on the analysis, the most likely causative agents of the disease are:
- **i. Virus** (common cause of respiratory symptoms)
- **iii. Conjugation Deficient Bacterium** (can also cause similar symptoms)
Therefore, the correct option indicating the pathogen is either a virus or a conjugation-deficient bacterium.
### Final Answer:
The correct options are **i. a virus** and **iii. a conjugation deficient bacterium**.
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