Multiple Choice
In the very first phase after the big bang, when the Universe was about a microsecond old, space was filled with____.
A) high-energy photons
B) protons and antiprotons
C) protons, neutrons, electrons, and positrons (anti-electrons)
D) electrons, and positrons (anti-electrons)
E) protons, neutrons, electrons
Correct Answer:

Verified
Correct Answer:
Verified
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