"all living organisms rely on for their energy needs"

The right answer that fits the blank space is: ATP (adenosine triphosphate)

Explanation:

This is the molecule that helps every living being to survive and fulfill its needs to pass their genes to the next generation. In humans, for example, this molecule is made in the process of respiration, where mitochondria is the main part of the process, but there are important things that happen before it occurs inside the mitochondria too, animals that use oxygen to produce energy are called aerobic. There are other organisms that don't use oxygen to produce energy, such as the Lactobacillus bulgaricus, these kinds of organisms are called anaerobic.

bacterium is not correct