Final answer:
Polyuria, polydipsia, and polyphagia are symptoms of diabetes mellitus, a disease where insulin-related issues cause elevated blood glucose levels and result in symptoms such as frequent urination and thirst.
Step-by-step explanation:
The symptoms of polyuria (excessive urination), polydipsia (excessive thirst), and polyphagia (excessive hunger) are indicators of diabetes mellitus. Diabetes mellitus is a disease characterized by problems with the hormone insulin, which is produced by the pancreas. This condition leads to elevated blood glucose levels. The kidneys respond to the high glucose levels by excreting more urine, which explains the symptom of polyuria. The loss of water through the urine leads to dehydration and triggers a sensation of thirst, resulting in polydipsia. The body's cells also experience a shortage of glucose, despite high blood glucose levels, because insulin is not effectively transporting the glucose into the cells. This shortage causes the sensation of hunger, or polyphagia.
Given the three mentioned symptoms, the correct answer to the question is A: Diabetes.