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?

The test tube will be most likely the one with yellowish color.
This happen because of the respiration process between the snail and Elodea. Actually, this will heavily affected by the control factors. The more elodea that exist in the incubation, the lower the amount of CO2 would be,

hope this helps

The answer is a because - is an direction