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: Pediatrics
Most likely etiology in 10 month old child with high grade fever since 7 days, with the following x-ray finding and not responding to ceftriaxone 
Select and explain. 
A. Streptococcus pneumoniae, B. Staphylococcus aureus, C. Mycoplasma, D. Respiratory Syncytial Virus
B: Staphylococcus aureus
Answer: B: Staphylococcus aureus 
Explanation: Streptococcus pneumoniae and staphylococcus aureus both can lead to consolidation of a lobe of lung as seen in the Chest x-ray. But Resistance to Ceftriaxone is seen in staphylococcus aureus only.