Question

students set up two test tubes with a nutrient solution and bacteria. the solution with the bacteria has a yellow, cloudy appearance. the students also add a chemical that tests for the presence of alcohol. if alcohol is present, the solution turns pink. test tube a is sealed with a rubber stopper to prevent oxygen from entering. test tube b is sealed with a rubber stopper and a tube that will pump a small amount of oxygen into the solution. the test tubes are sealed for a week. the table shows observations at the start of the experiment and after one week.

test tube	initial observations (start of experiment)	final observations (after 1 week)
b	yellow, cloudy	yellow, cloudy

based on the observations, which statement best explains one of the test tubes?
the bacteria in test tube b are in an aerobic environment where all oxygen has been removed, and the bacteria are producing energy through aerobic respiration.
the bacteria in test tube a have created an anaerobic environment where all oxygen has been removed, and the bacteria are producing energy using anaerobic respiration.
the bacteria in test tube b have created an anaerobic environment where oxygen is still present, and the bacteria are producing energy using aerobic respiration.
the bacteria in test tube a are in an aerobic environment where oxygen is present, and the bacteria are producing energy using anaerobic respiration.

Explanation:

Test Tube A turned pink, indicating alcohol presence. Anaerobic respiration by bacteria can produce alcohol. Test Tube A is sealed to prevent oxygen entry, creating an anaerobic environment. Test Tube B has oxygen pumped in and remains yellow, suggesting aerobic respiration where no alcohol is produced.

Answer:

The bacteria in Test Tube A have created an anaerobic environment where all oxygen has been removed, and the bacteria are producing energy using anaerobic respiration.