Write the full name for LPG and CNG.

44 How is petroleum gas obtained? Name the gas that is its main constituent. 45 Name any two components obtained by fractional distillation of petroleum that are not used as a fuel. 47 Name three characteristics of a fuel that determines its quality. 48 The heat produced by burning of cow dung cake of mass 210 g raised the temperature of 50 g of water by 2° C. Assuming that all the heat was utilized for heating water whose specific heat capacity is 4.2 J/g ° C, calculate the calorific value of the dung cake.