11. Which of the following drugs involves modification of the drug by enzymatic modification or degradation of its active element to alter its/their resistance?

A. Penicillins
B. Chloramphenicol
C. Aminoglycosides
D. All of these

12. Who developed the concept of specific toxicity?

A. Pasteur
B. Fleming
C. Watson
D. Ehrlich

13. When using alcohol as an antiseptic, which concentration is considered most effective?

A. 95%
B. 50%
C. 70%
D. 25%

14. Fluoroquinolones are antibiotics which inhibit

A. DNA polymerase
B. RNA polymerase
C. DNA gyrase
D. Cross-linking of peptidoglycan

15. Which of the following is used only in life-threatening situations when no other drug is adequate?

A. Penicillin
B. Tetracycline
C. Chloramphenicol
D. Streptomycin