The following aquariums were set up witht he same volume of water. (elodea is an awautic 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 oxyfen gas flow if placed in the ddark for serveral weeks

a: 1,2, and 3
b: 2 and 3
c: 3 only
d: none

None of the aquarium will establish a cycle of carbon dioxide and oxygen gas flow.

Explanation:

[Answer is eligible if any external oxygen source is not provided.]

Elodea is a green quatic plant which produces oxygen when it carries out photosynthesis. But here the plant is kept in the dark so no photosynthesis will take place and oxygen will not be produced. Oxygen in the water will be taken up for respiration by the plant. Thus, keeping only elodea will not establish a cycle.Keeping Elodea and snail in the aquarium will also not establish the cycle because photosynthesis is not taking place thus no oxygen will be produced by the plant. Respiration will occur in both the plant and the snail. Thus there will be increasing stress on oxygen level and at a point it will be negligible.Keeping an aquatic snail only will result in taking up of oxygen for respiration and release of carbon dioxide. Thus, no cycle is esatablished.

Nucleotides

Explanation:

DNA is a polymer of nucleotide monomers.

Nucleotides are made of a nitrogenous base (either adenine, thymine, guanine, or cytosine), a deoxyribose sugar, and a phosphate group.

The nucleotides are joined together by phosphodiester bonds between the sugar of one nucleotide and the phosphate group of the next.