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: Medicine
In cystic fibrosis the most common organism which causes infection is 
Select and explain. 
A. Pseudomonas, B. Staphylococcus, C. Kiebsiella, D. Streptococcus
B: Staphylococcus
Answer: B: Staphylococcus 
Explanation: Respiratory infections are characteristic feature of cystic fibrosis in the presence of viscous secretions blocking medium and small airways.The most common organism is Staphylococcus aureus.Other organisms include H.influenza,Pseudomonas aeruginosa,etc. Ref:Harrison's med:18th edition,page no:1697.