Final answer:
Rudolf Virchow articulated that new cells could only arise from pre-existing cells, establishing a central principle of the modern cell theory.
Step-by-step explanation:
Rudolf Virchow, a pathologist active around the mid-1800s, contributed significantly to our understanding of cellular biology. In an 1855 essay entitled "Cellular Pathology," he popularized the idea that new cells could only arise from pre-existing cells. This pivotal concept is now a central tenet of the modern cell theory, and emphasizes that cells do not spontaneously appear from inanimate substances, cosmic radiation, or the atmosphere but rather through the division of existing cells. This theory played a crucial role in biology and shifted the scientific understanding of how life perpetuates. Therefore, the correct answer to the question is B) Cells could only arise from pre-existing cells.