The correct option is A. hydro. Explanation of the Correct Answer Hydro Power: Hydro power refers to the energy generated from the movement of water, typically through dams or water turbines. This type of power is considered renewable and does not produce direct emissions or pollutants during its operation. The process involves harnessing the kinetic energy of flowing water to generate electricity, which can then be used to power various agricultural operations without releasing harmful substances into the environment. Why Hydro Power Does Not Cause Pollution:

1. Renewable Source: Hydro power relies on the natural water cycle, which is continuously replenished by rainfall and snowmelt. This means it does not deplete resources or contribute to environmental degradation.
2. No Emissions: Unlike fossil fuels, hydro power does not emit carbon dioxide (CO2) or other greenhouse gases during electricity generation. This significantly reduces its impact on air quality and climate change.
3. Minimal Waste: The primary byproduct of hydro power generation is water, which is returned to the environment. There are no harmful chemicals or pollutants released into the air or water.

Explanation of Why Other Options Are Incorrect B. Electrical: - While electrical power itself does not cause pollution, the source of the electricity can. If the electricity is generated from fossil fuels (like coal or natural gas), it can lead to significant air pollution and greenhouse gas emissions. Therefore, electrical power is not inherently pollution-free. C. Mechanical: - Mechanical power often refers to energy derived from machines that may run on fossil fuels or other non-renewable sources. For example, tractors and other farm machinery typically use diesel or gasoline, which release pollutants into the atmosphere. Thus, mechanical power can contribute to air pollution. D. Chemical: - Chemical power usually involves the use of fertilizers, pesticides, or other chemicals in agricultural practices. The application of these substances can lead to soil and water pollution, as runoff can contaminate local waterways and harm ecosystems. Therefore, chemical power is associated with significant environmental risks. Summary of Key Points

• Hydro power is renewable and does not produce emissions or pollutants during operation.
• Electrical power can be clean or polluting, depending on its source.
• Mechanical power often relies on fossil fuels, contributing to air pollution.
• Chemical power involves the use of fertilizers and pesticides, which can lead to environmental contamination.

Revision Summary

• Hydro power is pollution-free as it harnesses water energy without emissions.
• Electrical power's environmental impact depends on its generation source.
• Mechanical power typically involves fossil fuels, leading to pollution.
• Chemical power can cause soil and water pollution through agricultural chemicals.