People are beginning to use clean energy sources mainly because _______. A: fossil fuels have caused a lot of pollution B: clean energy is cheap C: fossil fuels have cost a lot of lives D: they do not have enough fossil fuels now

The burning of fossil fuels results in the pollution of the______.

智慧职教: ___ coal，the most important natural fuels are gas and oil.

Fossil fuels like coal, oil and natural gas are non-renewable energy sources.

Fuels of high quality with their earlier ignitions will cause higher （）pressure in cylinders of a diesel engine.

U3T204. Almost 90 percent of the world's energy is supplied through the ______ of fossil fuels,

U3T104. Known as externalities, the hidden costs of fossil fuels aren't ______ in their market price,

中国大学MOOC: Renewable energies are not competitive with fossil fuels in consideration of health and environmental cost.

We have to prepare for a new age of energy synthesis since fossil fuels will be eventually depleted.

Using some ________ fuels ,such as natural gas, in vehicles can generally00a000a0reduce harmful pollutants and exhaust emissions.