Aquatic fern which is an excellent biofertilizer used in paddy fields

Options

A. Azolla
B. Salvinia
C. Marsilea
D. Pteridium

Answer

**Step-by-Step Solution:**

1. **Identify the Question:** The question asks for the name of an aquatic fern that acts as an excellent biofertilizer specifically used in paddy fields.

2. **Understand the Options:** The options provided are Azolla, Salpina, Marcilia, and Teridium. We need to determine which of these is an aquatic fern and known for its role as a biofertilizer.

3. **Recall Characteristics of Each Option:**
- **Azolla:** This is a small aquatic fern that has a symbiotic relationship with nitrogen-fixing bacteria (Anabaena). It is commonly used in rice cultivation as a biofertilizer.
- **Salpina:** This is not widely recognized as a biofertilizer or an aquatic fern.
- **Marcilia:** This is also not commonly known for its use as a biofertilizer in paddy fields.
- **Teridium:** This is not an aquatic fern and does not serve as a biofertilizer.

4. **Conclude the Correct Answer:** Based on the characteristics and uses of the options, Azolla is the aquatic fern that is recognized as an excellent biofertilizer for paddy fields due to its ability to fix nitrogen.

5. **Final Answer:** The correct answer is **Azolla**.

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