The event that marks the beginning of the universe and left behind the cosmic microwave background radiation is known as the what?

• A. Steady State
• B. Cosmic Inflation
• C. Big Bang Theory
• D. Nucleosynthesis

Answer: (C)

The beginning of the universe is described by the Big Bang. It marks the moment expansion starts and sets the stage for all later cosmic evolution. The cosmic microwave background radiation is the afterglow left over from the early hot universe once it cooled enough for photons to travel freely (around 380,000 years after that start). This relic light provides a snapshot of the universe at that early time and is strong evidence for the Big Bang picture.

Other options don’t fit as well. A steady-state view imagines no single beginning, which wouldn’t naturally produce a specific, universal background glow like the CMB. Cosmic inflation refers to a rapid expansion phase very early on, but it’s a part of the Big Bang history, not the event that marks the universe’s start. Nucleosynthesis describes the formation of light elements shortly after the beginning, not the initial event itself.