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
All of the following DPP - 4 inhibitors should be used cautiously in renal insufficiency except? 
Select and explain. 
A. Sitagliptin, B. Vildagliptin, C. Linagliptin, D. Saxagliptin
C: Linagliptin
Answer: C: Linagliptin 
Explanation: Linagliptin is the only DPP - 4 inhibitor which is safe in renal failure patients.