Final answer:
The correct answer is option b. The M and N blood antigens are significant in paternity testing because they are fully developed at birth, allowing direct comparison with the alleged father's blood group and determining paternity.
Step-by-step explanation:
The M and N antigens are important for paternity testing because, unlike some other blood antigens, they are well developed at birth. This means that the M and N antigen phenotypes of a child can be compared directly with that of the alleged father to see if they match up, which can provide evidence for or against paternity. These antigens are part of the MNS blood group system, which is different from the ABO and Rh blood group systems but is still genetically inherited and can be used in paternity testing.
While the Rh factor is particularly important for the implications of Rh incompatibility between a mother and fetus, the M and N antigens do not change from the embryo stage and are not subject to the mother's antibodies, making them stable markers for paternity.