This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
A young boy of 18 years gets recurrent busts of otitis externa after swimming. Which of the following methods should be recommended? 
Select and explain. 
A. Not to swim, B. Use 2% acetic acid after swimming, C. Use ear drops containing an antibiotic and steroid, D. Use an antifungal ear drops after swimming
B: Use 2% acetic acid after swimming
Answer: B: Use 2% acetic acid after swimming 
Explanation: Use of 2% acetic acid or dilute alcohol is the most-effective method to prevent otitis externa after swimming. Antibiotic, antifungal or steroid containing drugs are not recommended for prophylaxis.