Which of the following best describes the nature of cosmic background radiation?

The nature of cosmic background radiation is best described as a remnant from the early universe. This radiation is a key piece of evidence supporting the Big Bang theory, which posits that the universe was once in a hot, dense state and has since expanded and cooled. The cosmic microwave background radiation fills the universe and is uniformly detected in all directions, representing the thermal radiation from when the universe became cool enough for protons and electrons to combine and form neutral hydrogen atoms about 380,000 years after the Big Bang. This remnant is not due to solar activity, which refers to phenomena occurring within our solar system, nor is it related to Earth's temperature or the movement of galaxies. Instead, it provides a snapshot of the early universe, making it a critical component for understanding cosmology and the origins of the universe.