An organic compound contains $78 \%$ (by wt.) carbon and remaining percentage of hydrogen. The right option for the empirical formula of this compound is : [Atomic wt. of $C$ is $12, H$ is 1$]$(1) $\mathrm{CH}$(2) $\mathrm{CH}_{2}$(3) $\mathrm{CH}_{3}$(4) $\mathrm{CH}_{4}$