Why Did the Era of Nuclei End When the Universe

question 11

Multiple Choice

Why did the era of nuclei end when the universe was about 380,000 years old?

• A)The universe had expanded and cooled enough for stable, neutral atoms to form.
• B)The nucleosynthesis era that produced the nuclei heavier than helium ended.
• C)All the free particles had combined to form the nuclei of atoms.
• D)Atomic nuclei were finally able to escape the plasma of the early universe.
• E)Photons were finally able to escape the plasma of the early universe and were no longer available to produce hydrogen and helium nuclei.