In which of the following pairs is the percentage of carbon the same?

$C_4H_6O_2$ does not represent :

Complete combustion of $750 \ g$ of an organic compound provides $420 \ g$ of $CO_2$ and $210 \ g$ of $H_2O$. The percentage composition of carbon and hydrogen in the organic compound is $15.3$ and ............. respectively. (Round off to the Nearest Integer)

In a compound,the ratio of masses of $H, C, O,$ and $N$ is $1:3:4:7$. The empirical formula is

$A$ compound possesses $8\%$ sulphur by mass. The least molecular mass is

The molecular mass of an organic compound is $108 \ g \ mol^{-1}$. If $C, H,$ and $N$ atoms are present in the weight ratio of $9 : 1 : 3.5$,what is the molecular formula?