You are answering a USMLE-style medical question. Question: A 41-year-old man presents to the emergency department with a 6-hour history of muscle cramping, decreased appetite, and diarrhea. He says that these symptoms came on rapidly but does not recall anything that may have triggered the episode. He has never experienced these symptoms before. His past medical history is significant for obesity, sleep apnea, and type 2 diabetes that is well controlled on metformin. He also has gastroesophageal reflux disease for which he occasionally takes antacids. On presentation he is found to have fast, shallow breathing and abdominal pain that is poorly localized. Basic labs as well as an arterial blood gas are obtained and the results are shown below: Na+: 139 mEq/L Cl-: 106 mEq/L HCO3-: 11 mEq/L pH: 7.25 pCO2: 22 mmHg Which of the following is the most likely cause of the changes seen in this patient's labs? Options: A) Anxiety B) Diarrhea C) Metformin D) Sleep apnea Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.