... . SOME EXPERTS ARE TRYING TO REVIVE HYDROELECTRIC POWER WHICH (...

5. ... . Some experts are trying to revive hydroelectric power which (derive) 6. ... from streams andrivers. Fifty years ago, hydroelectric power (provide) 7. ... one third of the electricity used in the UnitedStates, 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. Experimentsare also underway to make use of temperature differences in ocean water(produce) 10. .... energy.