Among the following,the most polar molecule is

Although both $CO_2$ and $H_2O$ are triatomic molecules,the shape of $H_2O$ molecule is bent while that of $CO_2$ is linear. Explain this on the basis of dipole moment.

Both $BF_3$ and $NH_3$ are covalent molecules. However,$BF_3$ is non-polar while $NH_3$ is polar. What is the reason for this?

Arrange the following molecules from most to least polar ($I$,$II$,$III$,$IV$,$V$ respectively): $CH_4$,$CF_2Cl_2$,$CF_2H_2$,$CCl_4$,$CCl_2H_2$.

Which of the following bonds is the most polar?

Which of the following molecules has a zero dipole moment?