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
Mechanism of action of Theophylline in bronchial asthma 
Select and explain. 
A. Phosphodiestesrase 4 inhibition, B. Beta 2 agonism, C. Antichoinergic action, D. Inhibition of mucociliary clearance
A: Phosphodiestesrase 4 inhibition
Answer: A: Phosphodiestesrase 4 inhibition 
Explanation: Refer Katzung 11/e p 345 Theophylline is used in bronchial asthma. It's mechanise of action is Inhibition of phosphodiestesrase paicularly PDE-4 Antagonism of adenosine receptors Enhancement for histone deacetylation