With increase in the temperature of carbonisation of coal ___________________?

A. Hydrogen content of coke oven gas increases due to cracking of hydrocarbons
B. Methane content in the coke oven gas decreases and carbon monoxide content increases
C. Calorific value of the coke oven gas decreases due to cracking of hydrocarbons which is not
compensated by increase in CO & H2 content
D. All A., B. and C.