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
Theophylline is a 
Select and explain. 
A. Mast cell stabilizer, B. Leukotriene antagonist, C. Phosphodiesterase inhibitor, D. Leukotriene synthesis inhibitor
C: Phosphodiesterase inhibitor
Answer: C: Phosphodiesterase inhibitor 
Explanation: Theophylline- Phosphodiesterase inhibitor (inhibit the degradation of CAMP) Sodium cromoglycate is a mast cell stabilizer used for prophylaxis of asthma Montelukast and zafirlukast are leukotriene antagonist Zileuton is a LOX inhibitor