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
A hypertensive patient has heart rate of 50 beats/min and taking tablet atenolol 200 mg/day in divided doses. After anaesthesia, heart rate further fell down to 40 beats/min. What will be the appropriate treatment to improve heart rate: 
Select and explain. 
A. IV adrenaline, B. IV atropine, C. IV isoprenaline, D. Dobutamine infusion intravenously
B: IV atropine
Answer: B: IV atropine 
Explanation: None