After the Big Bang,as the Universe Cooled and Protons and Electrons

Multiple Choice

After the Big Bang,as the universe cooled and protons and electrons combined so that the universe become neutral,what important consequence happened?

A) Photons began to travel freely through the universe.
B) Neutrinos ceased to interact with normal matter.
C) Dark matter ceased to interact with normal matter.
D) Protons and neutrons combined to form nuclei such as deuterium and helium.