The lab setup shows four test tubes. Tube 1 contains water only. Tube 2 contains a live snail. Tube 3 contains a live green water plant. Tube 4 contains both a live green water plant and a live snail.
In this setup, which tubes contain at least one organism carrying on cellular respiration?
A) Tubes 1 and 2 only.
B) Tubes 2 and 4 only.
C) Tubes 3 and 4 only.
D) Tubes 2, 3, and 4 only.