I. Fill in the passage: Non-renewable Fossil fuels nuclear dangerous converted turbines Alternative renewable exhausted At present, most of our energy comes from ________(oil, coal, and natural gas). However, they are _______energy sources. They will be ______within a relatively short time. Therefore, people must develop and use _______ sources of energy such as: wind, hydro, solar, _______. They are also called _______ energy sources. Hydro and nuclear power can generate a lot of energy. However, Hydro costs lots of money to build dams and nuclear is ______. The wind turns_______to make electricity. Solar energy can be _______ into electricity, too. It can be used to heat or cool our houses.