A compound contain equal mosses of the elements $A, B$ and $C$ if the atomic weights of $A, B$ and $C$ are 20 . 40 and 60 respectively. The empirical formula of the compound is

(A) $A_{3} B_{2} C$

(B) $\mathrm{AB}_{2} \mathrm{C}_{3}$

(C) ABC

(D) $\mathrm{A}_{6} \mathrm{B}_{3} \mathrm{C}_{2}$