Two competing models of the Universe's evolution are the Big Bang theory and the Steady State theory. Three major observational discoveries are:
I. The cosmological red-shift of distant galaxies.II. The Cosmic Microwave Background Radiation (CMBR).III. The primordial cosmic abundance ratio of helium-4 to hydrogen. \begin{aligned} &\text{I. The cosmological red-shift of distant galaxies.} \\ &\text{II. The Cosmic Microwave Background Radiation (CMBR).} \\ &\text{III. The primordial cosmic abundance ratio of helium-4 to hydrogen.} \end{aligned} I. The cosmological red-shift of distant galaxies.II. The Cosmic Microwave Background Radiation (CMBR).III. The primordial cosmic abundance ratio of helium-4 to hydrogen.Which of these discoveries can be explained by both theories, and which can only be explained by the Big Bang theory?
Both: I and III; Big Bang only: II
Both: I only; Big Bang only: II and III
Both: I and II; Big Bang only: III
Both: None; Big Bang only: I, II, and III