supernovas the big bang collisions of galaxies modern decay of unstable atoms
I gave my students this multiple choice question: Astronomers have found low-energy background radiation in every part of the sky that they have studied. This radiation is taken as evidence of energy remaining from which event?

Only one answer is correct among these 4 choices:
- supernovas
- the big bang
- collisions of galaxies
- modern decay of unstable atoms

Could you tell me which one is correct?

the big bang