For the following compounds, the correct statement(s) with respect to nucleophilic substitution reactions is(are)

 

Note that in examination condition or solvent is not given hence the extent/possibility increase.

(A) I & III follow $S_{N^1}$ mechanism ® correct

 (B) compound IV undergoes inversion of configuration

  (C) the order of reactivity for I, III & IV is IV > I > III ® correct

  (D) I & II follow $S_{N^2}$ Mechanism is correct