In Bombarding Atomic Nuclei with Proton "Bullets," the Protons Must

In bombarding atomic nuclei with proton "bullets," the protons must be accelerated to high energies to make contact with the target nuclei

A) because the target nuclei are so small.
B) because the target nuclei are negatively charged.
C) in order to penetrate through the electrons that surround each target nucleus.
D) because the target nuclei are positively charged.