Which Single Observation Is Perhaps the Strongest Argument Against the Steady-State

Multiple Choice

Which single observation is perhaps the strongest argument against the steady-state model of the universe and for the Big Bang model?

A) The number of supporters of the steady-state model is less than the number of supporters of the Big Bang model.
B) Astronomers have not observed matter being created from nothing in the space around Earth.
C) The universe is expanding.
D) The universe is bathed in a sea of microwaves coming from the edge of the visible universe.