Answer: No
Explanation: Since when a child is born it has DNA from both. As an example, the mom has brown hair, father has blonde hair, the child would take the DNA for the type of hair they get, either blonde or brown. So since its blood, the fathers is A, and the boy's is B, therefore it didn't take any of their DNA's so nope, he isn't the father.
I believe the answer is the first one you listed,
Hope this helps..
