Which of the following allowed Fleming to recognize the pattern of the Penicillium mold killing bacteria? A. He was a scientist trained in the craft of scientific observation.

B. He saw a similar pattern when he used an antibiotic to kill plated bacteria.

C. He knew that Penicillium killed bacteria, so he was prepared to make the observation.

D. He had previously seen a similar pattern when a tear fell on a Petri dish of bacteria.