This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Chloramphenicol, Subject name: Pharmacology
Mechanism of action of chloramphenicol is- 
Select and explain. 
A. Preventing binding of t RNA to ribosome, B. Cell wall lysis, C. cessation of peptide chain elongation, D. Inhibiting cell wall synthesis
C: cessation of peptide chain elongation
Answer: C: cessation of peptide chain elongation 
Explanation: Tetracyclines are the drugs that bind to 30S ribosomes and inhibit binding of aminoacyl tRNA to ribosomes. Chloramphenicol binds to 50S ribosome and interferes with peptide bond formation and transfer of peptide chain from p site to a site thereby inhibiting polypeptide elongation (Ref : essentials of medical pharmacology by KD Tripathy ) Chloramphenicol binds to 50S subunit--interferes with peptide bond formation and transfer of peptide chain from 'P' site.