What makes dark energy "dark"?
a. its unknown nature
b. its completely black color
c. its existence beyond the visible spectrum
d. its inevitable creation of a totally destructive big crunch
nucleosynthesis began when and ended when
a. the big bang occurred; the big crunch occurred
b. nuclear reactions could first occur; matter had condensed into galaxies and stars
c. the cosmic microwave background radiation formed; dark energy replaced it as the dominant energy form
d. the universe had cooled enough for atoms to combine; protons and neutrons were too far apart to form nuclei