Carbon dioxide with its two double bonds is an example of a polar molecule.
2 answers:
The bond between one carbon atom and one oxygen atom is polar but due to the fact that there is another oxygen attached to the carbon which has the same electronegativity value as the oxygen on the other side, the effect of polarity is canceled. 
is non-polar because the oxygens symmetrically alligned on the opposite sides of the carbon cancel the polarity effect.
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