Select the aquatic fern among the following options.

Options

A. Azolla
B. Salvinia
C. Salvia
D. Both (a) and (b)

Answer

To solve the question of selecting the aquatic fern among the given options, we can follow these steps:

### Step 1: Identify the Options
The options provided are:
1. Azolla
2. Salvinia
3. Salvia
4. Both A and B

### Step 2: Understand the Characteristics of Ferns
Ferns belong to the group known as pteridophytes. They are vascular plants that reproduce via spores. Some ferns are adapted to aquatic environments.

### Step 3: Analyze Each Option
- **Azolla**: This is a small aquatic fern that floats on water. It is known for its ability to form symbiotic relationships with cyanobacteria, which helps in nitrogen fixation. Azolla is indeed an aquatic fern.

- **Salvinia**: This is another type of aquatic fern that also floats on water. Like Azolla, it is adapted to aquatic environments and is classified as a pteridophyte. Therefore, Salvinia is also an aquatic fern.

- **Salvia**: This is not a fern; it is a genus of flowering plants in the mint family (Lamiaceae). Therefore, it does not qualify as an aquatic fern.

### Step 4: Determine the Correct Answer
Since both Azolla and Salvinia are aquatic ferns, the correct answer is:
**Both A and B**.

### Final Answer
The correct option is **4. Both A and B**.

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