A should be the answer because the more you test an experiment the more data you have to rely on changing the experiment would cause you to have different outcomes making the results different and unreliable so B, C, and D is not going to be the answer Hope this helps
It indicates that there is only one oxygen molecule
Nectar contains a high concentration of sucrose (sugar).
When hummingbirds ingest the nectar, their cells use oxygen to convert it into carbon dioxide and water.
The oxidation of sucrose releases a large amount of energy, which the birds can use for flapping their wings, etc.
