7. Which of the following SN2 reactions is the fastest?(A) CH3CH(Br)CH3 + HO- → CH3CH(OH)CH3 + Br- (B) CH3CH2CH2I + HO- → CH3CH2CH2OH + I- (C) CH3CH(I)CH3 + HO- → CH3CH(OH)CH3 + I- (D) CH3CH2CH2Br + HO- → CH3CH2CH2OH + Br- (E) CH3CH2CH2I + H2O → CH3CH2CH2OH + HI