Final answer:
The spread of antibiotic resistance is primarily driven by the inappropriate use of antibiotics, over prescription of antimicrobials, and excessive use in livestock. These practices lead to natural selection favoring resistant bacteria, which continue to multiply and can be transferred to humans.
Step-by-step explanation:
Factors that contribute to the spread of resistance to antibacterial drugs include C) Inappropriate use of antibiotics. This occurs when antibiotics are used when they are not needed, or when the full course of treatment is not completed. This leads to the survival of bacteria that are resistant to the antibiotics, which can then multiply and spread. Another factor is B) Widespread use of combination therapy, which can sometimes lead to resistance when multiple antibiotics are used unnecessarily. However, the option that most encapsulates the spread of resistance is inappropriate to use.
One of the main causes of antibiotic resistance is the overexposure to antibiotics. Antibiotics often prescribed unnecessarily contribute to the natural selection of resistant bacteria, leaving only resistant forms to proliferate. Other key factors include the overprescription of antimicrobials and the excessive use of antibiotics in livestock, both of which can maximize the probability of resistance developing and these resistant bacteria being transferred to humans.