Question: A 30-year-old patient presents to the clinic with complaints of excessive thirst and urination. The patient reports drinking several liters of water per day but continues to feel dehydrated. A physical examination reveals no significant findings, and the patient's vital signs are stable. Laboratory tests show elevated serum sodium levels and an osmolarity that is higher than expected for the measured serum sodium concentration. However, urine osmolarity is inappropriately low. Which of the following diagnostic tests would be able to confirm the likely diagnosis? Group of answer choices Serum glucose level Water deprivation test Serum potassium level Serum calcium level