The Sun and most stars are made almost entirely of a. hydrogen and carbon. b. helium and nitrogen. c. oxygen and nitrogen. d. helium and hydrogen.

So the question is what are the Sun and most stars almost entirely made of. So most stars, including our Sun are made out of hydrogen and helium. There is also a small percentage of oxygen, carbon and nitrogen and also very small quantities of iron, silicone and other metals. So the correct answer is d.