Scientists have used the big bang theory to make numerous predictions about the universe. One of their predictions is that about 75% of the visible matter in the universe should be hydrogen and about 25% should be helium. How could a scientist test this prediction?

A.
measure the amount of cosmic microwave background radiation in the universe
B.
analyze the spectra of electromagnetic radiation from stars and galaxies
C.
compare the number of galaxies with blueshifted spectra to those with redshifted spectra
D.
collect molecular samples from stars and galaxies to determine their composition