Answer: B- The drug caused the bacterium to change from being sensitive to being resistant to the drug.
Explanation: Drug resistance is due to the bacteria changing its genetic make up due to random mutations that renders the drug or antibiotic no longer bacteriocidal (effective in killing them). Drug resistant bacteria then survive and multiply, causing it to only be destroyed by a different kind of drug or by broad-spectrum antibiotics. Multiple drug resistant bacteria is the one that is no more susceptible to many different drugs, requiring development and production of a new drug which is very costly.
Drug resistant is often due to people not taking medication timeously and some not finishing their prescribed dosage.