A particular microbial pathogen that infects humans has a cell wall composed of peptidoglycan layer. An infection from this pathogen can easily be treated with an antibiotic that inhibits cell wall synthesis. A handwash containing this antibiotic was popularly used. In subsequent years, resistance to the antibiotic emerged in this pathogen. While one group evolved a modified cell wall, the other group evolved to survive without a cell wall. This type of selection is:

• Correct answer
  A

  Disruptive
• B

  Stabilising
• C

  Directional
• D

  Purifying

Hence, the correct answer is option: 'A'.