In the context of the history of cell biology and the development of cell theory, what was Louis Pasteur’s key contribution?

• A. He provided experimental evidence against spontaneous generation using swan-neck flask experiments, supporting the idea that cells arise from pre-existing cells.
• B. He discovered the cell nucleus and described it as a common feature of plant cells.
• C. He proposed that all living organisms are composed of cells as the basic unit of life.
• D. He first observed and named “cells” after viewing cork tissue under a microscope.

Answer: (A)