Which of the Effects Listed Below Is Not a Major $\approx$

Which of the effects listed below is not a major effect influencing the binding energy of the nucleus in the liquid-drop model?

A) The volume effect: the binding energy per nucleon is approximately constant when A > 50.
B) The surface effect: nucleons in the surface have fewer neighbours.
C) The quantum number effect: all nucleons in the nucleus have the same set of quantum numbers.
D) The Coulomb repulsion effect: protons repel protons.
E) The symmetry effect: stable nuclei tend to have N $\approx$ Z.