The microscopic proteinaceous infectious agents are called -

Options

A. protozoa
B. fungi
C. prions
D. bacteria

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term used to describe microscopic agents that are infectious and primarily composed of protein.

2. **Identifying Key Characteristics**: The key characteristics mentioned are:
- Microscopic
- Proteinaceous (made of protein)
- Infectious (capable of causing disease)

3. **Recalling Relevant Terms**: In biology, there are several types of infectious agents, including viruses, bacteria, and prions. Among these, prions are unique because they are solely made of protein and do not contain any nucleic acids (DNA or RNA).

4. **Defining Prions**: Prions are defined as misfolded proteins that can induce other normal proteins to also misfold, leading to disease. They are known to cause several neurodegenerative diseases in humans and animals.

5. **Conclusion**: Based on the characteristics and definition, the microscopic proteinaceous infectious agents are called **prions**.

---