This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Communicable diseases, Subject name: Social & Preventive Medicine
Why TB patient is recommend a regimen of 4 drugs on 1st visit - 
Select and explain. 
A. To avoid emergence of persistors, B. To avoid side effects, C. To cure early, D. None
A: To avoid emergence of persistors
Answer: A: To avoid emergence of persistors 
Explanation: During first visit (intensive phase) 3 or more drugs are combined to kill off as many bacilli as possible . The more rapidly the bacilli are killed initially, the less likely are "persisters" to emerge. The risk of relapse is also lessened. Ref: PARK&;S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICINE 23rd edition , Page :187