Correct Answer - D
When `EN` differnence =1.7 the bond is 50% ionic and 50% covalent if `EN` difference lt 1.7 the covlent character is more than 50% If `EN` difference gt 1.7 the ionic charater is more than 50% The `EN` difference between `A` and `B` is (4.0 -1.8) = 2.2 Therefore % ionic character is ~ 65% .