Read the following text and fill in each gap with a suitable the text.

Countries of the world rely heavily on petroleum, coal and natural gas for their energy sources. There are two major types of energy sources: renewable and non-renewable. Hydro-carbon or fossil fuels are non-renewable sources of energy. Reliance on them poses real big problems. First, fossil fuels such as oil, coal, gas, etc. are finite energy resources and the world eventually will run out of them.

Secondly, they will become too expensive in the coming decades and too damaging for the environment to repair. Thirdly, fossil fuels have direct polluting impacts on earth's environment causing global warming. In contrast, renewable energy sources such as, wind and solar energy are constantly and naturally replenished and never run out.

Most renewable energy comes either directly or indirectly from the sun. Sunlight or solar energy can be used for heating and lighting homes, for generating electricity and for other commercial and industrial uses.

(a) _________ dependence on fossil fuels poses a great threat (b)___________our environment. They are not (c)__________ So, they will become very expensive beside (d)__________ the cause the long-term shifts in temperatures and weather (e) ________.