Question

The following aquariums were set up with the same volume of water. (Elodea is an aquatic green plant.)
aquarium 1: Elodea only
aquarium 2: Elodea and an aquatic snail
aquarium 3: Aquatic snail only

Which aquariums will establish a cycle of carbon dioxide and oxygen gas flow if placed in the dark for several weeks?

Answer 1

A. 1, 2, and 3
B. 2 and 3
C. 3 only
D. none

Answer 2

In the dark, the Elodea will not perform photosynthesis - production of oxygen. It will only undergo the dark reaction.

Answer 3

So it's D?

Answer 4

I think that is the best option.