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: Pharmacology
Which of the following is used in beta–blocker overdose ? 
Select and explain. 
A. Atropine, B. Glucagon, C. Calcium chloride, D. All of these
D: All of these
Answer: D: All of these 
Explanation: None