This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
Which drugs action needs insulin presence to produce its therapeutic action? 
Select and explain. 
A. Glibenclamide, B. Nateglinide, C. Pioglitazone, D. Empagliflozin
C: Pioglitazone
Answer: C: Pioglitazone 
Explanation: Metformin and glitazones require insulin for their action as they are just insulin sensitizers not releasers. They sensitize the tissue to insulin hence require insulin for their action. Ref: KD Tripathi 8th ed.