The cosmic microwave background radiation was emitted during a time when ____ was the important process in the Universe.
A) recombination
B) ionization
C) fusion
D) antiproton production
E) positron production

Question

Quizplus · Accepted Answer

The cosmic microwave background radiation was emitted during the recombination era, when electrons combined with protons to form neutral hydrogen atoms, allowing photons to travel freely through space.

The Cosmic Microwave Background Radiation Was Emitted During a Time