The correct option is B Non-conventional energy
Energy
which is generated by using wind, tides, solar, geothermal heat, and biomass
including farm and animal waste as well as human excreta is known as
non-conventional energy. All these sources are renewable or inexhaustible and
do not cause environmental pollution. Bio-gas is an example for non-conventional
energy. It is based upon the use of dung to produce
gas which is used as domestic fuel especially in the rural areas. This
technique is based on the decomposition of organic matter in the absence of air
to yield gas consisting of methane (55%) and carbon dioxide (45%) which can be
used as a source of energy.