Ans. (b) Compressed Natural Gas (CNG) is the best and cheap fuel. It has replaced petrol and diesel fuel as it is considered a clean fuel. CNG consists of around 90% methane, by compressing it to less than 1% of the volume it occupies at standard atmospheric pressure. Propane and butane together form LPG or liquified petroleum gas while ethane is used in the chemical industry to produce ethene.
