Neutron Bombardment of Nuclei Typically Requires Lower Energies Than Proton

Neutron bombardment of nuclei typically requires lower energies than proton bombardment of nuclei. The energy difference is because

A) the strong nuclear force has a stronger attraction for the neutron.
B) gravity acts more strongly on the neutron.
C) the proton is attracted to the electron cloud.
D) the proton is repelled by the nucleus.
E) the electron cloud gives the proton a spiraling approach.