Answer:
the strong force that overcomes repulsion and keeps protons together
Step-by-step explanation:
The nucleus of an atom are made up of protons and neutrons. The protons habe positive charges while the neutrons have no charge. As a result of this, there is an electrostatic force of repulsion that exist within the nucleus.
Therefore, from the chart given which was meant to compare the strong and weak forces, Yanni's error was the strong force that overcomes repulsion and keeps protons together