Concept:The level of organization in an organism is based on whether its cells are arranged into specialized tissues or remain as independent cells.
Explanation:Spirogyra is a filamentous green alga made up of many cylindrical cells joined end to end.
These cells are similar in appearance and function.
Each cell can carry out all the basic life processes on its own.
Spirogyra does not possess true tissues, organs, or systems.
Although it is multicellular, its body shows only the cellular level of organization.
Thus, the correct classification is at the cell level.
Answer:C. Cell