Moss protonema resembles in structure
(a) Multicellular green alga
(b) Hypha of Rhizopus
(c) Unicellular structure of Acetabularia
(d) None of the above

Options

A. Multicellular green alga
B. Hypha of Rhizopus
C. Unicellular structure of Acetabularia
D. None of the above.

Answer

To solve the question "Moss protonema resembles in structure", we will analyze the options provided and determine which one is correct based on the characteristics of moss protonema.

### Step-by-Step Solution:

1. **Understand what Moss Protonema is**:
- Moss protonema is a thread-like structure that forms the early stage in the life cycle of mosses (which are bryophytes). It is composed of a filamentous arrangement of cells.

2. **Evaluate Option (a): Multicellular green alga**:
- Multicellular green algae often have a filamentous structure, which is similar to the thread-like structure of moss protonema. This resemblance makes this option a strong candidate.

3. **Evaluate Option (b): Hypha of Rhizopus**:
- Hyphae are the filamentous structures of fungi, such as Rhizopus. While they are also thread-like, they are fundamentally different in composition and function from moss protonema. Therefore, this option is incorrect.

4. **Evaluate Option (c): Unicellular structure of Acetabularia**:
- Acetabularia is a type of green algae that is unicellular and has a different structure compared to moss protonema. Since protonema is multicellular and filamentous, this option is also incorrect.

5. **Evaluate Option (d): None of the above**:
- Since we have identified that option (a) is correct, option (d) is not applicable.

6. **Conclusion**:
- Based on the analysis, the correct answer is **(a) Multicellular green alga**.

### Final Answer:
(a) Multicellular green alga