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: Surgery
Which of the following is not a self-retaining urinary catheter: March 2011 
Select and explain. 
A. Foley, B. Malecot, C. Gibbon, D. Red rubber
D: Red rubber
Answer: D: Red rubber 
Explanation: Ans. D: Red rubber