Which of the following compounds has a zero dipole moment?

Which of the following molecules have non-zero dipole moments?
$I$. Gauche conformation of $1, 2$-dibromoethane
$II$. Anti conformation of $1, 2$-dibromoethane
$III$. Trans-$1, 4$-dibromocyclohexane
$IV$. Cis-$1, 4$-dibromocyclohexane
$V$. Tetrabromomethane
$VI$. $1, 1$-dibromocyclohexane

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 is the correct order of dipole moments of $BF_3$,$NF_3$ and $NH_3$?

$A$ diatomic molecule has a dipole moment of $1.2 \, D$. If its bond length is equal to $10^{-10} \, m$,then the fraction of an electronic charge on each atom will be .............. $\%$

Which one of the following molecules is polar?