This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Quellung phenomenon is seen in: 
Select and explain. 
A. Pneumococcus, B. Streptococcus, C. Staphylococcus, D. Hemophilus
A: Pneumococcus
Answer: A: Pneumococcus 
Explanation: Ans. is 'a' i.e., Pneumococcus (Ref: Ananthanarayan, 8th/e, p. 220, 9th/e, p. 223)* A positive reaction shows clumping because of cross-linking of the antibodies and pneumococci. The halo effect around the pneumococci is apparent capsular swelling. A negative control would show no clumping or capsular swelling.