The search for alternative resources of energy (result) 1. ..... in various directions. Many communities (burn) 2. ... garbage and other biological waste products to produce electricity. Changing waste products into gases or oil is also an efficient way to dispose of waste. Experimental work (do) 3 ... to make synthetic fuels from coal, or coal tars. But to date, that process (prove) 4. .... expensive. Other experiments are underway to harness power with giant windmills. Geothermal power, heat from the earth, (also/ test) 5. ...... . Some experts are trying to revive hydroelectric power which (derive) 6. ....... from streams and rivers. Fifty years ago, hydroelectric power (provide) 7. ..... one third of the electricity used in the United States, but today it (supply) 8. ...... only four per cent. The oceans are another source of energy. Scientists (study) 9. ...... ways to change the energy of ocean currents, tides, and waves into electricity. Experiments are also underway to make use of temperature differences in ocean water (produce) 10. .... energy. Giái thích giùm mình luôn nhaa :))