Each of the following options contains a set of four molecules. Identify the option$(s)$ where all four molecules possess a permanent dipole moment at room temperature.
$(1)$ $BeCl_2, CO_2, BCl_3, CHCl_3$
$(2)$ $SO_2, C_6H_5Cl, H_2Se, BrF_5$
$(3)$ $BF_3, O_3, SF_6, XeF_6$
$(4)$ $NO_2, NH_3, POCl_3, CH_3Cl$

Experiments show that the $H_2O$ molecule has a dipole moment,while $CO_2$ does not. Which of the following structures best represents this fact?

Statement $I$: Dipole moment is a vector quantity and by convention it is depicted by a small arrow with tail on the positive centre and head pointing towards the negative centre.
Statement $II$: The crossed arrow of the dipole moment symbolizes the direction of the shift of charges in the molecules.
In the light of the above statements,choose the most appropriate answer from the options given below :-

Which has a permanent dipole moment?

The unequal sharing of bonded pair of electrons between two atoms in a molecule causes

Among $H_2S$, $H_2O$, $NF_3$, $NH_3$ and $CHCl_3$, identify the molecule $(X)$ with the lowest dipole moment value. The number of lone pairs of electrons present on the central atom of the molecule $(X)$ is: