In stars, energy is produced primarily as hydrogen atoms are combined to form a. helium atoms. c. oxygen atoms. b. carbon atoms. d. nitrogen atoms.

You are referring to nuclear fission where two Hydrogen nuclei combine to form Helium with a tremendous release of energy. This tremendous energy release in the early universe is believed to have caused the fusion of Helium into all of the heavier, naturally occuring elements.

the answer is b) helium atoms