The correct option is D Diabetes insipidus
Increased appetite and thirst, frequent urination are the major symptoms of diabetes mellitus and diabetes insipidus. When there is less amount of vasopressin, the rate of reabsorption of water in the kidney during urine formation, is decreased. Hence, excess amount of urine is excreted. This condition is known as diabetes insipidus. Whereas decreased production of insulin is main reason for diabetes mellitus.