You are answering a USMLE-style medical question. Question: An experimental new drug in the treatment of diabetes mellitus type 2 was found to increase the levels of incretins by preventing their degradation at the endothelium. This further increased glucose-dependent insulin production. Which of the following drugs has a mechanism of action most similar to this new experimental drug? Options: A) Sitagliptin B) Glimepiride C) Canagliflozin D) Pioglitazone Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.