The correct answer is OPTION C - repeatedly exposing a bacterial sample to the same antibiotic to see if the resistance changes.
Antibiotic resistance develops as a result of evolution via natural selection. When a bacteria sample is exposed repeatedly to the same antibiotic, certain bacteria in the sample may develop a from of mutation, which allows them to survive, and live on to reproduce. The surviving bacteria will then pass this trait to their offspring, thus evolving into a new drug-resistant strain, with a fully resistant generation of bacteria.