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-by-Step Solution:

1. **Identify the Group**: Recognize that ferns belong to the group known as Pteridophyta. This group includes various types of ferns and horsetails.

2. **Examine the Options**: Look at the given options in the question. The options include Azolla, Salvinia, and possibly other plants.

3. **Classify the Plants**:
- **Azolla**: Known as duckweed fern, it is a type of aquatic fern.
- **Salvinia**: Known as water moss, it is also classified as an aquatic fern.
- **Other Options**: If there are any other plants listed (like Salvia), they should be identified. Salvia is a flowering plant (angiosperm) and does not belong to the fern category.

4. **Differentiate Between the Aquatic Ferns**:
- Both Azolla and Salvinia are floating ferns.
- Azolla has roots, while Salvinia does not have a well-defined root system and can be considered an invasive weed in natural habitats.

5. **Conclude the Answer**: Since both Azolla and Salvinia are aquatic ferns, the correct answer to the question is that both A (Azolla) and B (Salvinia) are aquatic ferns.

### Final Answer:
The correct answer is **both A and B** (Azolla and Salvinia).

---