In 1859, Louis Pasteur designed an experiment to address the spontaneous generation. He used a curved-neck flask that allowed the air inside the flask to mix with air outside the flask, but prevented solid particles, like microorganisms, from entering the body of the flask. Compare and contrast the work of Pasteur and Spallanzani and explain how both men influenced the cell theory. A) They proved that cells cause disease. B) They proved that boiling kills microorganisms. C) They proved that plants, animals, fungi, protists, and bacteria are all made of cells. D) They proved that cells do not appear spontaneously, but only come from pre-existing cells.