<prompt> A woman whose blood type is A, Rh positive and a man whose blood type is B, Rh positive come to the clinic with a 3-year-old girl whose blood type is O, Rh negative. What can be said about the relationship of these two adults to this child?The woman can be the childs natural mother, but the man cannot be the natural fatherThe man can be the childs natural father, but the woman cannot be the natural motherNeither adult can be the natural parent of this childThis couple can be the natural parents of this child  <response>: Each parent needs only a single allele for either the A or B antigen or the RhD antigen to express these antigens on their blood cells and other cell types. Thus, if each parent also carries an allele for blood type O, as well as a null allele for the RhD antigen, then the child can be homozygous for the recessive O allele and the RhD-negative allele. 