Which Is Not True Concerning the Discovery and Development of the Penicillin

Which is not true concerning the discovery and development of the penicillin antibiotics?

A) Alexander Fleming noted that the mold Penicillium notatum inhibited bacterial growth
B) The first step in the development of these drugs was the isolation of the active agent produced by the mold Penicillium notatum
C) There are currently more than a dozen different penicillins in clinical use
D) World War I gave added impetus for the development of the penicillin antibiotics