29. In what way does the size of a star determine how far down the set of reactions of Question 26 stellar synthesis will proceed? What eventually happens to the star if it falls short of synthesis of iron? What happens eventually if it does synthesize iron in its interior?

30. How far down the set of stellar synthesis reactions will our own sun go?

31. Where did the heavy elements in our planet (and in the solar system) come from? Were they made in the interior of our sun?

32. Why is helium so rare on Earth, although common in the universe as a whole?

33. Why is the nitrogen content of the Earth less than in the entire universe, whereas the oxygen content is a thousand times greater?

34. Why is the composition of a living organism enriched in carbon and nitrogen relative to the other elements?