$(i)$ Name the four gases commonly present in biogas.
$(ii)$ List two advantages of using biogas over fossil fuels.

(N/A) $(i)$ The four gases commonly present in biogas are Methane $(CH_4)$,Carbon dioxide $(CO_2)$,Nitrogen $(N_2)$,and Hydrogen $(H_2)$.
$(ii)$ Two advantages of using biogas over fossil fuels are:
$(a)$ Biogas is a renewable source of energy as it is produced from biomass,whereas fossil fuels are non-renewable and finite.
$(b)$ Biogas is a clean fuel that does not cause significant air pollution upon burning,whereas the combustion of fossil fuels releases harmful pollutants like sulfur and nitrogen oxides,causing severe air pollution.