Which statement best describes the core principles of classical cell theory in the history of cell biology?

• A. Only multicellular organisms are made of cells, while unicellular organisms are not considered living.
• B. Cells originate spontaneously from nonliving matter under the right environmental conditions.
• C. All living organisms are composed of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.
• D. All cells contain a membrane-bound nucleus, and new cells form only by budding from the nucleus.

Answer: (C)