Ray fungi are

Options

A. actinomycetes
B. fungi
C. mycoplasma
D. archaebacteria

Answer

### Step-by-Step Solution:

1. **Understanding Ray Fungi**: The term "ray fungi" commonly refers to a specific group of organisms known as actinomycetes. This is the first step in identifying what ray fungi are.

2. **Characteristics of Actinomycetes**: Actinomycetes are unique because they exhibit characteristics of both fungi and bacteria. They form a mycelium, which consists of narrow hyphae. This is an important feature that distinguishes them from other prokaryotes.

3. **Role in Human Flora**: Actinomycetes are part of the normal flora in the human mouth. This means they are naturally occurring organisms that can be beneficial to human health.

4. **Antibiotic Production**: One of the significant contributions of actinomycetes is their ability to produce antibiotics. For example, they can produce streptomycin and actinomycin, which are important in medical treatments.

5. **Elimination of Other Options**:
- **Fungi**: While actinomycetes have fungal characteristics, they are not classified as true fungi.
- **Mycoplasma**: This is a different group of prokaryotes and does not fit the definition of ray fungi.
- **Archaebacteria**: This group also belongs to the kingdom Monera but is distinct from actinomycetes.

6. **Conclusion**: Based on the characteristics and roles of actinomycetes, the correct answer to the question "Ray fungi are" is **actinomycetes**.

### Final Answer:
Ray fungi are **actinomycetes**.

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