How did Louis Pasteur contribute to the development of cell theory?

• A. He provided experimental evidence against spontaneous generation, supporting the idea that cells come from pre-existing cells.
• B. He discovered the nucleus and showed it was essential for cell division.
• C. He first observed cells using a compound microscope and coined the term "cell."
• D. He proposed that all living organisms are composed of one or more cells and that the cell is the basic unit of life.

Answer: (A)