Write down nucleophilic substitution `(S_N2)` order for following.

The decreasing order of reactivity of the following compound towards nucleophilic substitution (S_N 2) is

Which is least reactive towards nucleophilic substitution (S_(N^(2)))

Which is least reactive towards nucleophilic substitution (S_(N^(2)))

Which is least reactive towards nucleophilic substitution (S_(N^(2)))

The order of reactivity of various alkyl halides towards nucleophilic substitution follows the order

The order of reactivity of various alkyl halides towards nucleophilic substitution follows the order

A dextrorotatory alkyl halide is allowed to react with nucleophile, leading to substitution via S_N2 mode only. The product obtained