A bacterium was grown in two test tubes filled with media rich in glucose. One tube was sealed to produce anaerobic conditions, and the other was not. A third uninoculated, unsealed tube was used as a control. Glucose utilization by this bacterium causes acid production, which is indicated by a lightening of the media color. If the bacterium is able to produce ATP only by aerobic respiration, we expect lightening of media in ________.a. lightening of media in the sealed tube only b. lightening of media in the unsealed tube only c. lightening of media in the sealed and unsealed tubes only d. lightening of media in the control tube only

According to the question, the bacteria can undergo only aerobic respiration, that is it can produce its energy, that is, ATP, or adenosine triphosphate, only in the presence of oxygen.
The unsealed tube allowed air or oxygen to pass into it which can be used by the bacteria for its respiration. In the process, it will produce acid that will cause the media colour to lighten.
The sealed tube do not allow any oxygen to pass into it. As the given bacteria can undergo only aerobic respiration but not anaerobic respiration, in absence of oxygen it will not be able to undergo respiration and produce energy and acid. Hence, the media colour will remain unchanged.
The control tube is used to check the sterility of the media.