It was one of Fleming's colleagues who identified the mould as penicillin. Fleming subsequently tested the penicillin on animals, with no ill effects, and also used it to cure a colleague's eye infection.
After his initial discovery, Fleming did little more than keep a supply of the mould and return to his routine work. It was tile scientists Howard Florey and Ernst Chain who developed penicillin further. Florey and Chain were chiefly responsible for the research which led to its success as a drug, although Fleming took most of the credit for the discovery and its subsequent development.
Fleming had discovered the first antibiotic. However, it was not until the research work of
Florey and Chain that penicillin could be produced as a drug. At first supplies of penicillin were very limited, but by World War II it was being mass-produced by American drugs industry, and given to all soldiers before active service.
When did Fleming move to London？

At the age of 31.
B. At the age of 13.
C. At the age of 16.
D. At the age of 17.