Drug-resistant populations of microbes arise when

a. synergy between medication occurs

b. exposure to drugs causes mutations that produce resistance

c. resistant cells become numerous in a population due to their greater vigor

d. exposure to drugs selectively kills sensitive cells, allowing overgrowth of resistant cells

e. the patient becomes immune to the drug

The correct option is D. Drug-resistant populations of microbes arise when exposure to drugs selectively kills sensitive cells, allowing overgrowth of resistant cells.

Explanation:

Drug - resistance can be described as a mechanism through which an organism can overcome the effect of a drug.

Usually, exposure of a drug again and again to a population of microbes will make the microbes resistant to that drug. The cells of the microbes undergo some change to overcome the effect of that particular drug.

A population of drug-resistant microbes might occur when the sensitive microbes get killed by the drug and resistant strains remain alive.