Working from an earlier discovery of Charpentier's, chemists Emmanuelle Charpentier and Jennifer Doudna--winners of the 2020 Nobel Prize in Chemistry--re-created and then reprogrammed the so-called "genetic scissors" of a species of DNA-cleaving bacteria ________ a tool that is revolutionizing the field of gene technology.

Which choice completes the text so that it conforms to the conventions of Standard English?