In an experiment, Tony placed a potted plant under a bell jar, completely sealing the jar to the table top. After placing a box over the bell jar for 24 hours, he measured the concentrations of oxygen and carbon dioxide in the gas in the jar. Which statement BEST describes the measurements he would find in the jar, compared with the concentrations of oxygen and carbon dioxide in the classroom air?

A. Oxygen concentration increased, carbon dioxide concentration decreased.
B. Dioxide concentration increased; oxygen concentration decreased.
C. Concentrations of both carbon dioxide and oxygen decreased.
D. Concentrations of both carbon dioxide and oxygen increased.

The statement that best describes what would happen is that carbon dioxide concentration would increase while oxygen concentration would decrease.

The potted plant being placed under the bell jar and sealed off means that it had no access to light for photosynthesis. Thus, the light-dependent reaction of photosynthesis and oxygen production would cease accordingly.

However, respiration would continue because the process is independent of light. This means that any available oxygen within the space of the plant would be utilized for respiration while carbon dioxide would be produced.

Thus, with time, the oxygen level in the jar would dwindle while carbon dioxide level would increase as compared to the classroom air.

More on photosynthesis, respiration, and light can be found here: https://brainly.com/question/9453066