Correct Response: A. The discovery of cosmic background radiation coming from all directions in space by Arnold Penzias and Robert Wilson provided the first observational evidence supporting the Big Bang theory of the universe. The Big Bang theory suggests the universe started with a massive explosion and rapid expansion. The discovery of a black hole at the center of the Milky Way (B) was based on observations of an intense radio source at the middle of the Milky Way galaxy and is not related to the work of Penzias and Wilson. The homogeneity and absolute size of the universe (C) is still a matter of conjecture and study. The bending of light by large gravitational fields (D) was first observed in 1919 during a solar eclipse, but had been proposed by Isaac Newton and later calculated by Albert Einstein.
