Which one is a Water Fern

Options

A. Azolla
B. Salvinia
C. Marsilea
D. All the above.

Answer

To determine which one is a water fern from the given options, follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Water Fern**:
- Water ferns are types of ferns that thrive in aquatic environments. They belong to the class Pteropsida within the division Pteridophyta.

2. **Analyze the Given Options**:
- The options provided are Azolla, Salvinia, and Marsilia. We need to evaluate each one to see if they are classified as water ferns.

3. **Evaluate Azolla**:
- Azolla is known as an aquatic fern. It is recognized as the smallest pteridophyte and is often used as a biofertilizer. Therefore, Azolla qualifies as a water fern.

4. **Evaluate Salvinia**:
- Salvinia is also classified as an aquatic fern. It is heterosporous and thrives in water environments. Thus, Salvinia is another example of a water fern.

5. **Evaluate Marsilia**:
- Marsilia is known to be an aquatic fern as well. It is sometimes referred to as the "Piper Watt" fern and grows in water. Therefore, Marsilia also qualifies as a water fern.

6. **Conclusion**:
- Since all three options (Azolla, Salvinia, and Marsilia) are aquatic ferns, the answer to the question "Which one is a water fern?" is **all of the above**.

### Final Answer:
**All of the above (Azolla, Salvinia, Marsilia) are water ferns.**

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