Final answer:
The simplest level of organization classified as living is the cell, as it is the fundamental unit capable of all necessary physiological functions for life.
Step-by-step explanation:
The simplest level of organization that can be classified as living is the cell. This is because a cell is the smallest unit of a living thing. Living organisms, whether made of one cell such as bacteria, or many cells like humans, are composed of cells as the basic building blocks. Each cell has the ability to perform all physiological functions necessary for life. Higher levels of organization such as tissues, organs, and organisms involve more complex structures that are made up of cells working together.