A. LOCKING B. PUTTING C. ENDANGERING D. LIMITINGB. READ THE PASSAG...

10. A. locking B. putting C. endangering D. limitingB. Read the passage then choose the most suitable answer for each questionThe search for alternative sources of energy has led in various directions. Many communitiesare burning garbage and other biological waste products to produce electricity. Converting wasteproducts to gases or oil is also an effective way to dispose of wastes.Experimental work is being done to derive synthetic fuels from coal, oil shale, and coal tars. Butto date, that process has proven expensive. Other experiments are underway to harness power withgiant windmills. Geothermal power, heat from the Earth, is also being tested.Some experts expect utility companies to revive hydroelectric power derived from streams andrivers. Fifty years ago hydro-electric power provided one-third of the electricity used in the UnitedStates, but today it supplies only 4 percent. The oceans are another potential source of energy.Scientists are studying ways to convert the energy of ocean currents, tides, and waves to electricity.Experiments are also underway to make use of temperature differences in ocean water to produceenergy.