Primary halides undergo SN2 reaction with aq. KOH. The reaction forms a transition state where the attacking nucleophile and leaving group both are partially bonded to carbon. (B)
3∘ alkyl halide undergoes nucleophilic substitution reaction via formation of a stable 3∘ carbocation. Thus, it shows SN1 reaction where rate of reaction depends only on concentration of substrate.
Primary halides prefer to undergo E2 elimination reaction.
The reaction path followed is mathrm‌E‌l reaction. ∴ The correct option is A→IV,B→I,C→II and D→ III.