Find the Combination of Conditions That Are the Best for S_N2

Find the combination of conditions that are the best for S_N2 reactions.

A) The substrate is a tertiary alkyl iodide,solvent is aprotic,polar and the nucleophile is a strong base.
B) The substrate is a primary alkyl iodide,solvent is aprotic,polar and the nucleophile is a strong base.
C) The substrate is a primary alkyl fluoride,solvent is protic,polar and the nucleophile is a strong base.
D) The substrate is a primary alkyl iodide,solvent is non-polar and the nucleophile is a weak base.
E) The substrate is a tertiary alkyl iodide,solvent is non-polar and the nucleophile is a strong base.