Introduction to Cosmology Example Exam Question

Lecture 7: Cosmological models

Briefly explain the significance of any TWO of the following in the establishment of the Hot Big Bang theory as the best cosmological model:
the abundances of 2H and 4He; [2.5]
radio source counts; [2.5]
the blackbody spectrum of the cosmic microwave background. [2.5]

(2005 Q2.)

Go to the hints and suggestions.