This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'DNA dependent RNA synthesis is inhibited by which of the following drug? \nSelect and explain. \nA. Rifampicin, B. Ethambutol, C. Colchicine, D. Chloromycetin', 'role': 'user'}, {'content': "Answer: A \nExplanation: Rifampicin is an antimycobacterial drug which exes both intracellular and extracellular bactericidal activity by binding to and inhibiting mycobacterial DNA-dependent RNA polymerase blocking RNA synthesis. Ethambutol is a bacteriostatic against M tuberculosis. It acts by inhibiting arabinosyl transferases involved in cell wall synthesis, which probably inhibits the formation of arabinogalactan and lipoarabinomannan. Colchicine has antimitotic effects, arrests cell division in G1 by interfering with microtubule and spindle formation. Ref: Harrison's principles of internal medicine 18e chapter 168.", 'role': 'assistant'}]