The potential energy of a pair of nucleons is minimum when they are separated by about : (A) $0.8 \times 10^{-15}\text{ m}$ (B) $0.8 \times 10^{-10}\text{ m}$ (C) $2.0 \times 10^{-13}\text{ m}$ (D) $2.0 \times 10^{-14}\text{ m}$