The amount of oxygen increased. The amount of oxygen decreased. The oxygen was transformed into water. The oxygen was transformed into carbon dioxide.
I gave my students this multiple choice question: A scientist put several different plants in a sealed container. Every hour, she checked the oxygen in the container to see if it changed. How did the oxygen in the container most likely change?

Only one answer is correct among these 4 choices:
- The amount of oxygen increased.
- The amount of oxygen decreased.
- The oxygen was transformed into water.
- The oxygen was transformed into carbon dioxide.

Could you tell me which one is correct?

The amount of oxygen increased.