This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pneumococci, Subject name: Microbiology
Gram positive, catalase negative cocci - 
Select and explain. 
A. Staph aureus, B. Staph epidermidis, C. Staph saprophyticus, D. Pneumococcus
D: Pneumococcus
Answer: D: Pneumococcus 
Explanation: Ans. is 'd' i.e., Pneumococcus