An Electron and Proton Are Separated By $1 \times 10 ^ { - 12 }$

An electron and proton are separated by $1 \times 10 ^ { - 12 }$ meters. The attractive force between the pair is

A) 2.5 mN.
B) 1.1 mN.
C) 0.23 mN.
D) 0.71 mN.