What Key Event Took Place During the Atomic Epoch

Multiple Choice

What key event took place during the atomic epoch?

A) The universe expanded and cooled enough to allow the first particles to appear.
B) The universe expanded and cooled enough for electrons to orbit protons.
C) The neutrinos were created.
D) Atoms in the universe collected to form stars and galaxies.
E) The universe underwent a brief period of rapid expansion.