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: Medicine
The biochemical marker for primary hyperparathyroidism is 
Select and explain. 
A. Hypercalcemia, B. Hypophosphatemia, C. Increased alkaline phosphatase levels, D. Increased ACTH
A: Hypercalcemia
Answer: A: Hypercalcemia 
Explanation: None