It is most economically and environmentally sound to focus water resource management on ... . a. cloud seeding and towing icebergs to arid regions b. developing desalination plants c. increasing the efficiency of the way we use water d. in

The most economically and environmentally sound option to focus water resource management on is: **c. increasing the efficiency of the way we use water.** Improving water efficiency helps to conserve existing water resources, reduces waste, and can often be achieved through relatively low-cost measures compared to large-scale infrastructure projects like desalination plants or cloud seeding. It also minimizes environmental impacts associated with excessive water extraction and use.