(i) In chlorobenzene, due to resonance, there is a partial double bond character, so bond length is short.
(ii) The dipole moment of chlorobenzene is lower as bond length is shorter (µ=q×d) due to resonance and sp2 hybridized carbon, it has less tendency to release electrons than the sp3 hybrid of C−Cl (in cyclohexyl chloride). Hence, chlorobenzene is more electronegative resulting in decrease in polarity of C−Cl bond.