There is now increasing concern about the world’s (1) _____, particularly about those involving fossil (2) ______. In less than a hundred years we shall probably (3) _____ all the present (4) ____ of oil and gas. The world’s coal (5) ____ should last longer but, once used, these cannot be (6) _____. It is important, therefore, that we should develop such alternative sources of energy as solar energy and nuclear energy as well as water and wind (7) _____ (classed as (8) _____ energy). Until these energy (9) ______ are widely used, it is important for developed countries to reduce energy (10) ______ as much as possible.