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
In a patient of orbital cellulitis, micro organism on culture show greenish colonies and optochin sensitivity. The most likely organism is - 
Select and explain. 
A. Strep. viridans, B. Staphylococcus, C. Pseudomonas, D. Pneumococcus
D: Pneumococcus
Answer: D: Pneumococcus 
Explanation: None