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
Parathormone secretion is stimulated by ? 
Select and explain. 
A. Increased serum Ca++, B. Decreased serum Ca++, C. Increased serum K+, D. Decreased serum K+
B: Decreased serum Ca++
Answer: B: Decreased serum Ca++ 
Explanation: Ans. is `b' i.e., Decreased serum Ca++