Let the average nuclear force exerted by a proton on a proton be \(\mathrm{F_{pp}},\) by a proton on a neutron be \(\mathrm{F_{pn}}\) and by a neutron on a neutron be \(\mathrm{F_{nn}}.\) When their separations are nearly \(1~\text{fm},\) then:
1. \( \mathrm{F}_{\mathrm{pp}}<\mathrm{F}_{\mathrm{pn}}<\mathrm{F}_{\mathrm{nn}} \)
2. \( \mathrm{F}_{\mathrm{pn}}>\mathrm{F}_{\mathrm{pp}}>\mathrm{F}_{\mathrm{nn}} \)
3. \( \mathrm{F}_{\mathrm{pp}}>\mathrm{F}_{\mathrm{pn}}>\mathrm{F}_{\mathrm{nn}} \)
4. \(\mathrm{F}_{\mathrm{pp}}=\mathrm{F}_{\mathrm{pn}}=\mathrm{F}_{\mathrm{nn}}\)