Why is the era of nucleosynthesis so important in determining the chemical composition of the universe? a) all the elements except hydrogen were produced after the era of nucleosynthesis. b) we can observe spectra from this era to determine what the primordial mix of the elements was at the beginning of the universe. c) except for the small amount of matter produced later by stars, the chemical composition of the universe is the same now as at the end of the era of nucleosynthesis. d) we can study the processes that occurred during the era of nucleosynthesis to determine how most of the elements in the universe were created. e) by knowing how much matter was created during the era of nucleosynthesis, we can determine whether the universe is open or closed.