The dipole moment of a polar molecule depends upon its geometry. A symmetrical molecule is non-polar even though it contain polar bonds. Methane molecule $\left({\mathrm{CH}}_4\right)$ has zero value of dipole moment to its symmetric structure. We know that the bond dipole moment of $\mathrm{C}-\mathrm{H}$ bond of $\mathrm{C}-\mathrm{Cl}$ bond reinforce one another.

In ${\mathrm{CHCl}}_3$the resultant of $\mathrm{C}-\mathrm{H}\text{ and }\mathrm{C}-\mathrm{Cl}$ dipoles while in ${\mathrm{CH}}_2{\mathrm{Cl}}_2$, the resultant of C - H dipoles adds to resultant of two $\mathrm{C}-\mathrm{Cl}$ In case is highest among the given compounds. The molecule $\left({\mathrm{CCl}}_4\right)$ again becomes symmetrical and dipole moment reduces to zero.