Scientists placed frogs in a closed aquarium. They measured the amount of oxygen and carbon dioxide in the aquarium. The graph above shows their results. What most likely happened? A: The frogs used oxygen to make sugar and gave off carbon dioxide.
B: The frogs used carbon dioxide to make sugar and gave off oxygen.
C: The frogs used oxygen to get energy from sugar and gave off carbon dioxide.
D:The frogs used carbon dioxide to get energy from sugar and gave off oxygen.