Answer:
Stephen is not his biological father.
Step-by-step explanation:
DNA fingerprinting is a technique use to determine the DNA sequence of an individual organism. Short tandem repeats are unique among the individuals ans used to identify the individual in population.
The George DNA fingerprinting shows that he has STRs length of 6 and 7. Stephen's STRs does not match with his son George whereas Mary shows some similarities with George STRs. This indicates that Stephen is not the biological father of George because the biological father's STRs must match with the children STRs.
Thus, the correct answer is option (a).