Passive immunity was discovered by

Options

A. Edward Jenner
B. Emil von Behring
C. Robert Koch
D. Louis Pasteur

Explanation

To answer the question "Passive immunity was discovered by," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Passive Immunity**:
- Passive immunity refers to the immunity that is acquired when a person is given antibodies rather than producing them through their own immune system. This can occur naturally, such as when a newborn receives antibodies from the mother through the placenta or breast milk.

2. **Identifying Key Figures in Immunology**:
- The question provides four names: Edward Jenner, Emil von Behring, Robert Koch, and Louis Pasteur. Each of these scientists made significant contributions to immunology and medicine.

3. **Researching Contributions**:
- Edward Jenner is known for developing the smallpox vaccine, which is an example of active immunity.
- Robert Koch is famous for his work in bacteriology and identifying the causative agents of diseases.
- Louis Pasteur is renowned for his work on vaccines, including rabies and anthrax, but he is not specifically associated with passive immunity.
- Emil von Behring is recognized for his work on serum therapy and the discovery of passive immunity.

4. **Conclusion**:
- Based on the contributions of the scientists mentioned, the correct answer to the question is **Emil von Behring**, as he discovered passive immunity.

### Final Answer:
Passive immunity was discovered by **Emil von Behring**.