Uranium Decomposes Radioactively to Form Thorium Atomic Number 90) by Emitting

Uranium decomposes radioactively to form thorium atomic number 90) by emitting an α particle from its nucleus. The force of repulsion between the thorium nucleus and the α particle when the distance between them is 9.0 fm is approximately

A) 7.2 fN.
B) 57 nN.
C) 4.6 pN.
D) 1.02 kN.
E) 0.51 kN.