Answer:
Option B, exposing the bacteria to an antibiotic that kills cells lacking the plasmid
Step-by-step explanation:
Bacteria that have plasmid are selected from the ones that do not plasmid by placing them on antibiotics plates. As the bacteria that have plasmid within it will possess an antibiotic resistant gene due to which they are able to survive on the antibiotics plate and form colonies. While the bacteria that do not have plasmid die. These colonies of plasmid bacteria’s are grown to make large cultures from which plasmid protein is derived.