Which of the following terms describes the leftover radiation from the early universe?

The term that describes the leftover radiation from the early universe is cosmic background radiation. This radiation is a relic from the Big Bang, providing critical evidence for the Big Bang theory. As the universe expanded and cooled, it emitted energy that has now transformed into microwave radiation, detectable in all directions in the universe.

Detecting this cosmic microwave background radiation helps scientists understand the early stages of the universe and its evolution over time. It serves as a snapshot of the universe when it was just about 380,000 years old, marking the point at which matter began to form into atoms and light could travel freely across space. This radiation is uniform and isotropic, meaning it is the same in all directions, which aligns with the predictions of the Big Bang model.

The other terms listed, such as electromagnetic spectrum, refer to the broad range of all types of electromagnetic radiation, including visible light, ultraviolet, and infrared, rather than specific radiation from the early universe. Stellar radiation pertains to the light and energy emitted from stars, while gamma radiation is a high-energy form of electromagnetic radiation emitted during radioactive decay or in astrophysical processes, but neither relate specifically to the early universe's radiation relics.