Which of the test tubes shown below were most likely produced by a sprig of Elodea and a snail in the dark after 24 hours of incubation?

Answer:
The correct answer is - test tube 4.
Explanation:
The sprig of Elodea produces carbon dioxide and oxygen after the incubation of 24 hours whereas the snail releases the oxygen in the test tube during the incubation period. The presence of both gases gives a yellowish color to the test tube solution.
Incubation is the process in which organisms or anything at a precise environment and temperature so it can develop properly.
Thus, the correct answer is- test tube 4.