The Discovery of the Cosmic Microwave Background Was Important Because

The discovery of the cosmic microwave background was important because:

A) it established a firm center of the Universe.
B) it was experimental verification of a prediction from the Big Bang theory.
C) it proved that astronomy at radio wavelengths was possible.
D) its detection was a major advance in microwave testing.
E) it showed the universe must be closed, with more than the critical density here.