A scientist places a plant in a sealed container and measures the amount of carbon dioxide and oxygen present. For the first several days, she keeps the plant in the light and finds the oxygen concentration increases. For the next several days, she keeps the plant in the dark and notices the oxygen concentration decreases. Which of the following best explains why the oxygen concentration decreases in the dark?
A. The plant used the oxygen for photosynthesis.
B. The plant used the oxygen for cellular respiration.
C. The plant produced more carbon dioxide, displacing the oxygen.
D. The plant consumed more carbon dioxide, resulting in more oxygen use.
E. The container was probably not sealed properly.
Answer: E