Which of the following molecules has zero dipole moment?

Which of the following molecules has the highest dipole moment?

If the $HCl$ molecule were completely polar,the expected dipole moment would be $6.12 \ D$,but the experimental value of the dipole moment is $1.03 \ D$. What is the percentage of ionic character (in $\%$)?

Bond distance in $HF$ is $9.17 \times 10^{-11} \ m$. Dipole moment of $HF$ is $6.104 \times 10^{-30} \ Cm$. The percentage ionic character in $HF$ will be : .............. $\%$
(electron charge $= 1.60 \times 10^{-19} \ C$)

$A$ 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 .............. $\%$

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,$CO_2$.