The best reason for why a covalent bond forms is... Group of answer choices

a two atoms exist as ions and the ions are attracted to each other.

b the atoms that form cations have low ionization energy and anions have high electron affinity, so the two atoms exchange electrons.

c nonmetal atoms cannot react with each other unless they share electrons.

d atoms with high electronegativities will not lose electrons, so instead they share electrons to reach a stable number of valence electrons.