Which of the Following Have a Smallest Net Force

Which of the following have a smallest net force?

A) A 1-C charge a distance of 1 m from a -2-C charge.
B) A 1-C charge a distance of 0.5 m from a -1-C charge.
C) A 1-C charge exactly halfway between a -1-C charge and a 1-C charge separated by 2 m.
D) A 1-C charge exactly halfway between two -2-C charges separated by 2 m.
E) A 1-C charge a distance of 2m from a -4-C charge.