which bond is most polar? you will have to look up a table of electronegativies to answer this question.
Carbon is least electronegative so its attraction for electrons will be least so it will have a greater positive charge and alternatively fluorine will have a greater negative charge, so F-C bond is most polar. In F-N ,nitrogen will have lesser positive charge than carbon and fluorine will have a lesser negative charge as compared to in F-C and so on.