Final answer:
A paternity test is the most accurate method to determine if a man with blood group O and married to a woman of blood group AB is the father of a child with blood group AB. Blood type compatibility alone is not sufficient to confirm paternity.
Step-by-step explanation:
When determining whether a man with blood group O and married to a woman of blood group AB is the father of a child with blood group AB, a paternity test is the most accurate method. A paternity test compares the child's DNA with the potential father's DNA to determine if there is a biological relationship. Blood type compatibility alone cannot confirm paternity, as there are multiple possible combinations of blood types that can lead to the same blood type of the child. Genetic counseling can provide guidance and information, but it cannot determine paternity solely based on blood types. Astrology is not a scientific method and cannot be used to determine paternity or any other scientific question.