1. The problem statement, all variables and given/known data Ok, these questions are very simple but they are really bugging me and I would greatly appreciate an explanation. Question 1 is "which of the following elements must have been made in stars". The options are hydrogen, helium, carbon, oxygen and iron. Question 2 is "which of the following elements may not have been formed in either stars or supernovae". Options are hydrogen, helium, carbon, gold and iron. 2. Relevant equations None. 3. The attempt at a solution The answer in the book for Q1 only accepts carbon, oxygen and iron. Stars fuse hydrogen into helium for most of their life so how is this not also made inside stars? The only thing I can think of is that hydrogen and helium were formed in the early universe whilst the other three were not and therefore must be made in stars? I really don't know. Answer for Q2 only accepts hydrogen and helium. I get hydrogen as it is not technically formed in a star (it is the fuel) but why is helium not formed in a star. Or is it the wording where they say 'may' and 'or' meaning that helium is formed in a star but not in a supernova. Thanks for any help offered.