I Thought That the Big Bang Was Hot! If the Cosmic

I thought that the Big Bang was hot! If the cosmic microwave background radiation is the radiation left over from the Big Bang, why then is it only 3 K?

A) The Big Bang itself was hot, but the temperature decreased as the universe expanded, and the temperature now is 3 K.
B) It is not from the Big Bang itself-it is from cold, intergalactic hydrogen clouds that are left over from the Big Bang.
C) The Big Bang itself was hot, but by the time the universe became transparent the temperature had already decreased to 3 K.
D) The Big Bang was not hot-its temperature was the same as we observe it now from the cosmic background radiation.