A gaseous alkane was exploded with oxygen.The volume of $O_2$ for complete combustion to $CO_2$ formed was in the ratio of 7 : 4.The molecular formula of alkane is

Question

$\begin{array}{1 1}(a)\;CH_4&(b)\;C_2H_6\\(c)\;C_3H_6&(d)\;C_4H_{10}\end{array}$