Which best describes the “Recombination Event” in the early history of the universe?

a. Matter and Anti-matter combined to make highly energetic photons for the first time

b. Free electrons became bound to nuclei to form neutral atoms for the second time

c. Atoms were re-ionized after the formation of the first generation of stars

d. Free electrons became bound to nuclei to form neutral atoms for the first time

e. The universe cooled enough for quarks to be confined in nuclei for the first time