The theory says that the big bang produced the chemical elements hydrogen and helium. what evidence supports this?

One of the biggest evidence that big bang produced hydrogen and helium is the Cosmic Background radiation proof. CBR is basically the matter and antimatter energy released  during the Big Bang. The evidence of CBR are apparent as a radio signal which have a temperature of 2.7 K. Also, through extensive spectroscopic surveys  from distant stars and galaxies , it is found that hydrogen and helium  make up  all the matter in the universe.  Hydrogen accounts for 74%  while helium contributes 25% of the total mass.  

it's unlikely a majority of a large population would agree on issues

hope this : )