Let `F_pp, F_pn and F_nn` denote the magnitudes of the nuclear force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron respectively. When the separation is `1 fm`,
A. `F_(pp) gt F_(pn)=F_(n n)`
B. `F_(pp)=F_(pn)=F_(n n)`
C. `F_(pp) gt F_(pn) gt F_(n n)`
D. `F_(pp) lt F_(pn)=F_(n n)`