15. What was the final volume of each balloon after 120 minutes?
16. Based on the results, what was the best source of energy (e.g., food) for the yeast?
17. Based on the results, what was the worst source of energy (e.g., food) for the yeast?
18. What factors (ingredients) negatively affected the growth of yeast?
19. What is the name for the type of fermentation that yeast use?
20. List two commercial uses of fermentation.