Consider an Sn2 reaction of NaSH in a polar aprotic solvent with (CH3)2CHCH2CH2X. What would be the relative order of reactivity for the following X substituents?
I. X= I II. X=Br III. X=Cl IV. X=F
A. I>II>III>IV
B.II>I>IV>III
C.IV>III>II>I
D.III>I>II>IV
E. None of these choices