Which one of the following statements is correct ?

Options

A. Extensive use of chemical fertilizers may lead to eutrophication of nearby water bodies
B. Both Azotobacter and Rhizobium fix atmospheric nitrogen in root nodules of plant
C. Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphates and potassium for plant nutrition in soil
D. At present, it is not possible to grow maize without chemical fertilizers

Answer

To determine which statement is correct, we will analyze each statement provided in the question.

### Step-by-Step Solution:

1. **Analyze the First Statement**:
- The first statement claims that "extensive use of chemical fertilizers may lead to the eutrophication of nearby water bodies."
- This statement is correct. The excessive use of chemical fertilizers can lead to nutrient runoff into water bodies, causing algal blooms. These blooms deplete oxygen in the water, harming aquatic life, which is a process known as eutrophication.

2. **Analyze the Second Statement**:
- The second statement states that "both Azotobacter and Rhizobium fix atmospheric nitrogen in the root nodules of plants."
- This statement is incorrect. While Rhizobium does form symbiotic relationships with the root nodules of leguminous plants to fix nitrogen, Azotobacter is a free-living bacterium that does not form nodules. It fixes nitrogen in the soil.

3. **Analyze the Third Statement**:
- The third statement claims that "Cyanobacteria such as Anabaena and Nostoc are important mobilizers of phosphate and potassium for plant nutrition in soil."
- This statement is also incorrect. Cyanobacteria are primarily known for their ability to fix atmospheric nitrogen, not for mobilizing phosphate and potassium.

4. **Analyze the Fourth Statement**:
- The fourth statement says, "At present, it is not possible to grow maize without chemical fertilizers."
- This statement is incorrect. Maize can be grown without chemical fertilizers by using organic methods, such as organic manure and compost, which is part of organic farming practices.

### Conclusion:
After analyzing all the statements, the only correct statement is the **first statement** regarding the eutrophication caused by the extensive use of chemical fertilizers.

### Final Answer:
The correct statement is: **The extensive use of chemical fertilizers may lead to the eutrophication of nearby water bodies.**

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