If a GC separation is performed on a nonpolar and slightly more polar column (same length), which of the following sentences is most correct. Please explain your answer. a) On a more polar column, nonpolar compounds will have shorter retention times. b) On a more polar column, all molecules will have longer retention times. c) On a more polar column, retention times will be unchanged. d) On a more polar column, molecules that are more polar will have longer ret. times.