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
Father has a blood group B ; Mother has AB ; Children are not likely to have the following blood group: 
Select and explain. 
A. O, B. A, C. B, D. AB
A: O
Answer: A: O 
Explanation: Answer is A (Blood group O) : There is just no way that children might have blood group 0. The answer is obvious so please excuse me on in explanation to this one.