Concept:Stirring/loosening soil mainly improves air supply, water entry, and weed control.Explanation:• Stirring breaks up compact soil, so air can enter easily — I is correct.• Loose soil allows water to penetrate more easily — III is correct.• Stirring uproots or buries weeds, thus reducing weed growth — IV is correct.• Increasing the activities of soil organisms is not a direct/main purpose of stirring — II is not correct.Answer:B. I, III and IV only