In his 2003 speech at Rice University’s Energy & Nanotechnology Conference, the late Nobel Laureate Richard Smalley highlighted the ____10 problems for the next 50 years. In his list,_______sits at the top, and water comes next. Now, with the price of solar power going down, the dawn of a new energy _____is just around the corner. As a result, ________ is going to be the greatest challenge for humanity.But the water problem is complicated. First, unlike coal and oil, water cannot be _______. Second, water is intertwined with every other sector of society. Third, while water demands are growing, climate change is intensifying droughts and floods and water supplies are fluctuating.There are solutions, such as building water-transfer aqueducts, hydroelectric dams, and desalination plants. But they may be incredibly expensive. It will take time for scientists to find affordable solutions to the water problem. Before that, everyone should do his or her bit to conserve water.