This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
The following is used for exocytosis 
Select and explain. 
A. Calcium, B. Sodium, C. Potassium, D. All
A: Calcium
Answer: A: Calcium 
Explanation: Calcium plays an impoant role in exocytosis Exocytosis is an active vesicular transpo system