The reactivity of alkyl bromides.
Towards iodide ion in dry acetone decrease in the order

• Correct answer
  A

  IV $>$ I $>$ II $>$ III
• B

  I $>$ IV $>$ II $>$ III
• C

  III $>$ II $>$ I $>1$
• D

  III $>$ II $>$ IV $>$ I

Solution

In dry acetone reaction follows $\mathrm{SN}^2$ mechanism Hence,

Hence, the correct answer is option: 'A'.