(a)
(i) Reduce: Less use of natural resources/ avoid wastage of food, water, electricity etc.
(ii)Recycle: Collection of materials like plastic, glass, metals, paper etc. and recycle these materials to make required items instead of synthesizing fresh ones. This would save natural resources
(iii) Reuse: Still better than recycling as no energy is required here and the already used things /items are used again and again.
(b)
(i) Essential for living organisms
(ii) It has limited availability
(iii) Conservation of water allows its equitable distribution.
(iv) Essential for sustainable development