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: Medicine
Increased susceptibility to disease due to V. cholerae, Shigella, E. coli O157, and norovirus is seen in which blood groups? 
Select and explain. 
A. AB, B. A, C. B, D. O
D: O
Answer: D: O 
Explanation: People with blood group O has increased susceptibility to to V. cholerae, Shigella, E. coli O157, and norovirus. Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 1085