... from any source of energy. If we didn't waste so (47) _____ energy, our resources would last longer. Unless we do research on (48) _____ energy, wind power, wave power, tidal power, hydroelectric ... survive 26. By cutting down the trees, people destroy the ecosystem of the rain forest ____ . a. on which they depend b. where they depend on c. which they depend d. where they depend 27. _________comes ... natural resources then? Every year we mine millions of tons of coal, use millions of barrels of oil, and cut down thousands of acres of forests. But the earth produces only a limited amount of these...