The correct option is "1 and 3 only" because reduced or zero tillage and retaining crop residue directly contribute to water conservation in agriculture. Reduced tillage helps maintain soil structure and moisture retention, while crop residues act as a protective layer that minimizes evaporation, enhances soil health, and reduces the need for additional irrigation. Conversely, applying gypsum primarily improves soil structure and nutrient availability but does not specifically target water conservation, making it less relevant in this context.