A carrier is a human being that

Options

A. Functions as a reservior of infection
B. Possesses pathogen but is not harmed
C. Contains antibodies sufficient enough to balance the antigen
D. All the above

Answer

To answer the question "A carrier is a human being that," we need to analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Definition of a Carrier**:
- A carrier is an individual who harbors a pathogen (such as a virus or bacterium) but does not exhibit symptoms of the disease caused by that pathogen. This means they can still spread the infection to others.

2. **Evaluating Option A**:
- **Option A: Functions as a reservoir of infection**.
- This is true because carriers can serve as reservoirs where the infectious agent lives and multiplies without causing harm to the carrier.

3. **Evaluating Option B**:
- **Option B: Possesses pathogen but is not harmed**.
- This is also true. Carriers can possess the pathogen without showing any signs of illness, indicating that they are not harmed by it.

4. **Evaluating Option C**:
- **Option C: Contains antibodies sufficient enough to balance the antigen**.
- This is correct as well. A carrier may have developed antibodies against the pathogen, which helps them to not get sick while still carrying the pathogen.

5. **Conclusion**:
- Since all the options (A, B, and C) correctly describe characteristics of a carrier, the correct answer is:
- **Option D: All of the above**.

### Final Answer:
The correct answer is **Option D: All of the above**.

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