The compound that will contain the most polar bond is D. chloroethane, H3CCH2Cl. This is because the bond between the carbon and chlorine atoms is more polar than the bonds between the carbon and hydrogen atoms in the other compounds. The polarity of a bond is determined by the difference in electronegativity between the atoms involved in the bond. Chlorine has a higher electronegativity than carbon, so the bond between them will be more polar. The other compounds listed have bonds between carbon and hydrogen atoms, which have a smaller difference in electronegativity and are therefore less polar.