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
A patient of renal failure has been diagnosed with cholera, so which of the tetracyclines is most suitable for the patient: 
Select and explain. 
A. Minocycline., B. Doxycycline., C. Oxytetracycline., D. All of the above.
B: Doxycycline.
Answer: B: Doxycycline. 
Explanation: All tetracyclines are excreted primarily in the urine except doxycycline. Doxycycline is excreted in the faeces and thus can be used in the presence of renal failure.