Which S_N2 Reaction Will Occur Most Rapidly in Aqueous Acetone $\to$

Which S_N2 reaction will occur most rapidly in aqueous acetone solution? Assume concentrations and temperature are the same in each instance.

A) HO^- + CH₃-Cl $\to$ CH₃OH + Cl^-
B) HO^- + CH₃CH₂-Cl $\to$ CH₃CH₂OH + Cl^-
C) HO^- + (CH₃) ₂CH-Cl $\to$ (CH₃) ₂CHOH + Cl^-
D) HO^- + (CH₃) ₃C-Cl $\to$ (CH₃) ₃COH + Cl^-
E) HO^- + (CH₃) ₃CCH₂-Cl $\to$ (CH₃) ₃CCH₂OH + Cl^-