Sarita noticed that her potted plant was not healthy. She put few earthworms into the pot. After few days, she noticed that her plant looked healthier. Which of the following could not be the possible reason for this?
(i) The earthworms ate up all the pests and weeds in the soil. (ii) The earthworms helped the plant to absorb more carbon dioxide from atmosphere. (iii) The earthworms synthesised nitrogen for the plant, (iv) The earthworms improved the texture of pot soil, increased the air content of the soil and nutrient availability to the plant.

Options

A. (i) and (ii) only
B. (i), (ii) and (iii) only
C. (iv) only
D. (i) and (iv) only

Explanation

**Step-by-Step Solution:**

1. **Understanding the Role of Earthworms**:
Earthworms are known to improve soil health. They help in aerating the soil, enhancing its texture, and increasing nutrient availability. They consume organic matter, which contributes to the formation of humus, a vital component of healthy soil.

2. **Analyzing Each Option**:
- **(i) The earthworms ate up all the pests and weeds in the soil**: This statement is incorrect. Earthworms do not eat pests or weeds; they primarily consume organic matter and help in decomposing it.
- **(ii) The earthworms helped the plant to absorb more carbon dioxide from the atmosphere**: This statement is misleading. While earthworms improve soil aeration, they do not directly help plants absorb carbon dioxide from the atmosphere.
- **(iii) The earthworms synthesised nitrogen for the plant**: This statement is also incorrect. Earthworms do not synthesize nitrogen; they do not have the ability to fix atmospheric nitrogen like some bacteria do.
- **(iv) The earthworms improved the texture of pot soil, increased the air content of the soil and nutrient availability to the plant**: This statement is correct. Earthworms do improve soil texture and increase nutrient availability.

3. **Identifying the Incorrect Reason**:
From the analysis, options (i) and (iii) are incorrect. However, the question asks for the reason that could not be a possible reason for the plant's health improvement. The most definitive incorrect option is (iii) because earthworms do not synthesize nitrogen.

4. **Conclusion**:
Therefore, the answer is **(iii) The earthworms synthesised nitrogen for the plant**.

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