Answer:
C) Valence electrons.
Step-by-step explanation:
When a chemical bond is formed it is the electrons that are shared and it is they that hold the two atoms together due to the coulomb forces between the positive nuclei and the valence electrons. To put in in another way, both nuclei of the bond want the electrons, but neither can get them, regardless, they hold on to them, and this is what makes a chemical bond.