Which of the following compounds does not possess a dipole moment?

$(a)$ Discuss the significance/applications of dipole moment.
$(b)$ Represent diagrammatically the bond moments and the resultant dipole moment in $CO_2, NF_3$ and $CHCl_3$.

The dipole moment of $o-$,$p-$ and $m-$dichlorobenzene will be in the order:

Which of the following are arranged in the decreasing order of dipole moment?

The set of molecules among the following with zero dipole moment is $CCl_4$,$BF_3$,$CHCl_3$,$CS_2$,$NH_3$,$1,4$-dichlorobenzene,$CO_2$.

Assertion : Molecules of larger size have higher polarizability.
Reason : Polarizability is observed only in those molecules which have a permanent dipole moment.