Read this passage.
In 1928, Scottish scientist Alexander Fleming discovered penicillin. This discovery proved to be a crucial contribution to the medical field.
Which sentence could be added to the passage and maintain its formal style?
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After people started using penicillin to treat infections, they got better fast.
Afterwards, you could use penicillin in all sorts of ways to stop you from getting sick.
Doctors soon began to use penicillin to treat infections in patients.
Pretty soon, penicillin was being used in a bunch of stuff that treats infections.
