This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Greatest stimulator for ADH secretion: 
Select and explain. 
A. Hyperosmolarity, B. Hyponatremia, C. Hypotension, D. Hypovolemia
A: Hyperosmolarity
Answer: A: Hyperosmolarity 
Explanation: A i.e. Hyperosmolarity