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: Microbiology
[{'content': 'In a patient of orbital cellulitis, micro organism on culture show greenish colonies and optochin sensitivity. The most likely organism is : \nSelect and explain. \nA. Strep. viridans, B. Staphylococcus, C. Pseudomonas, D. Pneumococcus', 'role': 'user'}, {'content': 'Answer: D \nExplanation: “Pneumococci is optochin sensitive and forms green colonies on blood agar due to Α hemolysis.”\nCharacteristic features of Pneumococci :\n\nBile soluble, optochin sensitive\nInulin fermenter\nCapsulated, shows quellung reaction\nColonies show central umbonation, appear as draughtsmann or carrom coin\nMC causative agent of lobar Pneumonia, Adult meningitis, otitis media, sinusitis (orbital cellulitis is complication of sinusitis).', 'role': 'assistant'}]