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': 'Which anti TB drug cause resistance fastest? \nSelect and explain. \nA. INH, B. Streptomycin, C. Rifampicin, D. Ethambutol', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e., INH "In patient on antitubercular drugs initial resistance occurs in about 4% of isolates, usually to isoniazid".', 'role': 'assistant'}]