Hint: Contour ploughing is a practice of farming of the planting across a slope that is following its elevation contour lines by creating a water break that reduces the formation of gullies during heavy precipitation.
Contour ploughing is a method of soil conservation. The prevention of depletion of the topmost layer of the soil due to erosion for preventing the reduced fertility which is caused by over usage, salinization, acidification, and other chemical soil contamination is soil conservation. The loss of nutrients and a sequel to deforestation and typical desertification are large scale erosion. soil conservation can be improved using crop rotation and conservation tillage which affect both erosion and fertility. The farming with soil conservation involves green manures and other soil enhancing practices which make the soil to be equalized and attempt to mimic the biology of barren lands. They help with reviving the damaged soil and eliminate the use of nitrogen fertilizer or fungicide which helps with the production of above-average yields and protects the crops during drought or flooding.
Water conservation: It is the preservation of water that constitutes all the strategies and activities to manage the natural resources of water and to protect the hydrosphere for the current and future human demand. Climate change has increased pressures on natural water resources with manufacturing and agricultural irrigation. It ensures the availability of water for future generations and for not exceeding its not natural placement. Water conservation takes place to avoid damage to water quality.
Air pollution: It is caused due to the particles present in the air which are harmful to the health of humans and others by causing damage to the climate and other materials. It can cause severe diseases and allergies which can cause death to humans and other living beings. The air pollution gets generated due to the damage to the natural or built environment.
So, the correct answer is option (b) 'Soil conservation'.
Note: About 2.6 billion tons of soil get lost each year and the rate of loss is 10 times faster than the replenishment of the soil. To reduce the soil erosion best management practices are proven for the replenishment and the improvement of environmental quality.