This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Pharmacology
Which of the following drugs has been found to be useful in acute severe asthma 
Select and explain. 
A. Magnesium sulphate, B. Anti-leukotriene, C. Cromolymln sodium, D. Cyclosporine
A: Magnesium sulphate
Answer: A: Magnesium sulphate 
Explanation: Magnesium sulphate by Iv or inhalation route has been used for the treatment big acute severe asthma All other drugs mentioned in the options are used for prophylaxis of asthma Refer Harrison 17/e p 1605