Select the correct statement with respect to disease.

Options

A. Injection of snake antivenom against snakebite is an example of active immunisation.
B. Certain protozoans have been used to produce Hepatities - B vaccine
C. If B and T - lymphocytes are destroyed due to an unknown reason, the body will not be able to produce antibodies against a pathogen
D. Injection of dead / inactivaed pathogen causes passive immunity.

Answer

To solve the question regarding the correct statement with respect to disease, we need to analyze each of the provided statements carefully.

### Step-by-Step Solution:

1. **Understanding Immunity**:
- Immunity can be classified into two main types: **Active Immunity** and **Passive Immunity**.
- **Active Immunity**: This occurs when the body is exposed to an antigen and produces its own antibodies in response. This can happen through vaccination.
- **Passive Immunity**: This involves the direct transfer of antibodies from one individual to another, providing immediate but temporary protection. An example is the administration of antivenom.

2. **Analyzing the First Statement**:
- The first statement claims that the injection of snake antivenom against a snake bite is an example of active immunization.
- **Analysis**: This statement is **false** because snake antivenom is an example of passive immunity, not active immunity. It contains ready-made antibodies.

3. **Analyzing the Second Statement**:
- The second statement suggests that certain protozoans have been used to produce the hepatitis B vaccine.
- **Analysis**: This statement is also **false**. Hepatitis B is caused by a virus, not protozoans, so protozoans cannot be used to produce the vaccine.

4. **Analyzing the Third Statement**:
- The third statement states that if B and T lymphocytes are destroyed due to an unknown reason, the body will not be able to produce antibodies against a pathogen.
- **Analysis**: This statement is **true**. B and T lymphocytes are essential for the immune response, including the production of antibodies.

5. **Analyzing the Fourth Statement**:
- The fourth statement claims that the injection of dead inactivated pathogens causes passive immunity.
- **Analysis**: This statement is **false**. The injection of dead or inactivated pathogens actually leads to active immunity, as the body generates its own immune response.

6. **Conclusion**:
- After analyzing all statements, the only correct statement is the third one, which indicates that if B and T lymphocytes are destroyed, the body will not be able to produce antibodies.

### Final Answer:
The correct statement with respect to disease is: **If B and T lymphocytes are destroyed due to an unknown reason, the body will not be able to produce antibodies against a pathogen.**

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