$F_{pp}$,$F_{nn}$,and $F_{np}$ are the nuclear forces between proton-proton,neutron-neutron,and neutron-proton respectively. Then the relation between them is:

• A
  $F_{pp} = F_{nn} \neq F_{np}$
• B
  $F_{pp} \neq F_{nn} = F_{np}$
• C
  $F_{pp} = F_{nn} = F_{np}$
• D
  $F_{pp} \neq F_{nn} \neq F_{np}$