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
In a patient of known prolonged congenital QT syndrome and intermittent Torsade-de-pointes, which of the following should be prescribed? 
Select and explain. 
A. Magnesium sulphate, B. Metoprolol, C. Cardiac pacing, D. Isoprendine
B: Metoprolol
Answer: B: Metoprolol 
Explanation: Ans. is 'b' i.e., Metoprolol