Because you cannot test it or observe it.
A scientific theory are created through the scientific method, in the scientific method you need to be able observe it and experiment.
The correct answer is a eukaryotic cell. The eukaryotic cell is a bacteria cell that has the same structure as more complex cells. Eukaryotic cells have many structures that help to maintain homeostasis and also to provide energy for the protein synthesis.
Answer: ATP (adenosine tri-phosphate) supplies energy for cellular activities when one of its phosphate bonds is broken.
