Which of the following is example of active immunity:

Options

A. Foetus receives antibodies from mother through placenta during pregnancy.
B. Colostrum secreted by mother during initial days of lactation has abundant antibodies to protect the infant.
C. Injecting the microbes deliberately during immunisation.
D. All of the above.

Answer

To determine which of the given options is an example of active immunity, we need to understand the definitions of active and passive immunity.

### Step-by-Step Solution:

1. **Define Active Immunity**:
Active immunity occurs when the body produces its own antibodies in response to an antigen (like a pathogen or vaccine). This can happen naturally (through infection) or artificially (through vaccination).

2. **Define Passive Immunity**:
Passive immunity is when antibodies are transferred from one individual to another, and the recipient's immune system does not produce its own antibodies. This can occur naturally (e.g., antibodies from mother to fetus) or artificially (e.g., through antibody injections).

3. **Analyze the Options**:
- **Option 1**: "Fetus receives antibody from mother through placenta during pregnancy."
- This is an example of passive immunity because the fetus is receiving pre-formed antibodies (IgG) from the mother.

- **Option 2**: "Colostrum secreted by mother during initial days of lactation has abundant antibodies to protect the infant."
- This is also an example of passive immunity as the infant is receiving pre-formed antibodies (IgA) from the mother’s milk.

- **Option 3**: "Injecting the microbes deliberately during immunization."
- This is an example of active immunity. When a vaccine is administered, it stimulates the immune system to produce its own antibodies against the pathogens present in the vaccine.

4. **Conclusion**:
The correct answer is the third option: "Injecting the microbes deliberately during immunization," as it leads to the production of antibodies by the individual's own immune system, which is characteristic of active immunity.

### Final Answer:
The example of active immunity is "Injecting the microbes deliberately during immunization."

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