Question

reinforcing exercise
in 1928, bacteriologist alexander fleming was studying staphylococcus, a type of bacteria that can cause serious infections. he grew the bacteria on small cylinders called petri dishes. one day, an accident that he had accidentally left a petri dish with some of the 1928 culture was not cleaned up. he found that there were no bacteria around the moldy area. fleming correctly decided that the mold had had an antibacterial effect, something that prevented the bacteria from growing. fleming identified the mold as the fungus penicillium notatum and named its antibacterial component - which he was unable to chemically isolate - penicillin. flemings discovery of penicillins bacterial effect led to the amazing finding that it could be used to treat infections. several years after his initial observation, scientists built on his work by extracting penicillin from mold and demonstrating its effectiveness as a treatment.
what is the main, or central, idea of this passage?
fleming realized that when a strain of mold inadvertently came into contact with a petri dish, the mold prevented bacterial growth.
fleming’s chance observation of the antibacterial properties of mold led to the discovery of penicillin as a treatment.
fleming came up with the name for penicillin, the bacteria - fighting ingredient in the penicillium notatum mold.

Explanation:

The passage outlines Alexander Fleming's accidental observation that mold inhibited bacterial growth, his identification of its antibacterial component penicillin, and how this led to penicillin being developed as an infection treatment. The central idea encompasses the chance observation and the resulting discovery of penicillin as a treatment.

Answer:

Fleming's chance observation of the antibacterial properties of mold led to the discovery of penicillin as a treatment.