The Discovery That the Sun and Similar Stars Consist of About

The discovery that the Sun and similar stars consist of about 25% helium posed a dilemma: There was too much helium in the universe to be accounted for by nucleosynthesis in stars in the contemporary cosmological models. How was this dilemma resolved?

A) The universe was found to be older than originally thought, thus allowing more time for stars to produce helium.
B) New helium-producing reactions were discovered in addition to the usual hydrogen-to-helium reaction.
C) It was discovered that earlier generations of stars were larger and hotter than previously thought and thus able to produce more helium.
D) The early universe was found to be hot and dense enough to produce helium from hydrogen, even before the first stars were formed.