Answer: (A)Dr Alexander Flemming noticed the mould inhibiting bacterial growth in a Petri dish.
Step-by-step explanation:
In 1928 Dr. Flemming returned from a holiday to discover that mould had grown on a Petri dish he had not stored properly; noticing that the mould (now called penicillin) was stopping bacterial growth on the dish. The bacteria on the dish was staphylococcus.
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