Correct Option
The correct option is (c).
Explanation
Modern agricultural practices, while essential for food production, often generate significant negative environmental externalities. These include water pollution through chemical run-off, air pollution from residue management, and health hazards associated with the handling of toxic agrochemicals.Statement 1 is Correct: The excessive application of chemical fertilisers results in surface run-off into nearby water bodies. The accumulation of nutrients, particularly nitrogen and phosphorus, causes eutrophication. This process stimulates dense algal blooms that deplete dissolved oxygen in the water, leading to the death of aquatic organisms and degradation of water quality.
Statement 2 is Incorrect: The burning of crop residues (stubble burning) is a detrimental environmental practice. It releases large quantities of particulate matter (PM), carbon dioxide ($CO_2$), carbon monoxide ($CO$), and oxides of nitrogen and sulphur into the atmosphere. Combustion consumes oxygen; it does not enrich the air with it.
Statement 3 is Correct: Weedicides (herbicides) are toxic chemical substances designed to eliminate unwanted vegetation. If handled without proper protective gear, they can cause acute and chronic health issues in farmers, including skin irritation, respiratory problems, and systemic toxicity.
Key Takeaway: Sustainable agriculture requires managing the trade-offs between productivity and environmental health, specifically addressing the risks of eutrophication from fertilisers and air pollution from stubble burning.