For which pair of the fuel gases, calorific value $($C$.$V$.)$ of one fuel is almost double that of the other on volume basis $($i$.$e$.,$ kcal$/$Nm$3)$ while the C$.$V$.$ is same on weight basis $($i$.$e$.,$ kcal$/$kg$)?$

Propane and acetylene

Propane and LPG

Sewage gas and gobar gas

B$.$F gas and coke oven gas