Final answer:
The frequency of antibiotic-resistant bacteria decreases when the bacterial population is no longer exposed to the antibiotic due to the significant impact of bacterial antibiotic resistance mechanisms on the population.
Step-by-step explanation:
The frequency of antibiotic-resistant bacteria tends to go down when the bacterial population is no longer being exposed to the antibiotic. This is because bacterial antibiotic resistance mechanisms have a significant impact on the bacterial population. When antibiotics are present, they selectively kill off bacteria that do not have the resistance gene. This results in a population dominated by antibiotic-resistant bacteria.