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

$CO_2$ is a non-polar molecule $(\mu = 0)$ whereas $SO_2$ is polar $(\mu = 1.62 \ D)$. This difference is due to the fact that:

$BF_3$ and $NF_3$ are both covalent compounds. However,$BF_3$ is non-polar,while $NF_3$ is polar because .....

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 of the following compounds exhibits a dipole moment?

Which one of the following molecules is polar?