This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Medicine
Which one of the following is the best stimulus for the release of the Arginine-vasopressin? 
Select and explain. 
A. Hypertonicity, B. Hypokalemia, C. Intravascular volume depletion, D. Hypernatremia
A: Hypertonicity
Answer: A: Hypertonicity 
Explanation: (A) Hypertonicity