Directions: Rearrange the following five sentences (A), (B), (C), (D), and (E) in the proper sequence to form a meaningful paragraph, then answer the questions below them.

A. The discovery of cosmic microwave background radiation constitutes a major development in modern physical cosmology.

B. There had been a prior measurement of the cosmic background radiation (CMB) by Andrew McKellar in 1941 at an effective temperature of 2.3 K using CN stellar absorption lines observed by W. S. Adams.

C. The new measurements were accepted as important evidence for a hot early Universe and as evidence against the rival steady-state theory as theoretical work around 1950 showed the need for a CMB for consistency with the simplest relativistic universe models.

D. Although no reference to the CMB is made by McKellar, it was not until much later after the Penzias and Wilson measurements that the significance of this measurement was understood.

E. In 1964, US physicist Arno Allan Penzias and radio-astronomer Robert Woodrow Wilson discovered the CMB, estimating its temperature as 3.5 K, as they experimented with the Holmdel Horn Antenna.