15 c.c. of gaseous hydrocarbon required 45 c.c. of oxygen for complete combustion and 30 c.c. of carbon dioxide is formed. The formula of the hydrocarbon is

General Reaction of Combustion is

$C_x{H}_y+\left(x+\frac{y}{4}\right)O_2\to x{CO}_2+\frac{y}{2}{H}_{2}O$

Volume of oxygen required is 3 times that of hydrocarbon for formation of ${CO}_2$ which has volume twice  that of Hydrocarbon.

Hence, $x=2; x+\frac{y}{4}=3;y=4$ 

Formula of the Hydrocarbon is $C_2{H}_4$. 

Hence, option (D) is correct.