CO2 is not polar as in this case the same types of molecules
are pulling in the same as well as opposite direction. CH4 is also not polar as
there is no imbalance in the charge of the molecules. CBr4 is also not polar
because in this case also no imbalance in the molecular charges can be seen.
CHBr3 is a bit polar in nature because it has different kind of charges at its
opposite ends. S among the all 4 options CHBr3 is polar.