Final answer:
The electrostatic force causes the protons within the nucleus to repel each other, but the nucleus is held together by the much stronger strong nuclear force.
Step-by-step explanation:
The question asks about the role of the electrostatic force within the nucleus of an atom. The correct answer to the question is C: It causes the protons to repel each other. This effect is due to the fact that protons are all positively charged, and like charges repel each other due to electrostatic force. However, despite this repulsion, the nucleus does not fly apart because the strong nuclear force, which is much more powerful at short ranges, acts between protons, and between protons and neutrons, holding them together despite the electrostatic repulsion. The strong nuclear force is approximately 100 times stronger than electromagnetism at the distances involved within the nucleus. Consequently, the electrostatic force does not add to the strong nuclear force, nor does it hold the protons and neutrons together, nor does it cancel out the strong nuclear force.