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
The following drug is NOT useful during acute attack of bronchial asthma : 
Select and explain. 
A. Salbutamol, B. Hydrocortisone, C. Cromolyn sodium, D. Theophylline
C: Cromolyn sodium
Answer: C: Cromolyn sodium 
Explanation: None