Answer:
A child with type B blood can have a mother with type B blood and a father with type O blood so the judge grants her request and decides due to Susan is right and Craig must pay child support (option b).
Step-by-step explanation:
Susan is right in this case because her son with type B blood may have a mother with type B blood and a father with type O blood. 
Blood types, according to the ABO system, depend on the existence of surface antigens A or B —Types A, B and AB— or their absence in the erythrocyte membrane. 
In the inheritance of blood groups A and B are co-dominant, while the absence of antigens —type O— is a recessive trait. 
Assuming that Susan has a genotype B/B and that Craig has a genotype O/O: 
Alleles O O 
B B/O B/O 
B B/O B/O 
So it is very likely that the child is Craig's son and Susan is right.