While performing routine postpartum testing for an Rh immune globulin (RhIG) candidate, a weakly positive antibody screening test was found. Anti-D was identified. This antibody is most likely the result of:
A. Massive fetomaternal hemorrhage occurring at the time of this delivery
B. Antenatal administration of Rh immune globulin at 28 weeks gestation
C. Contamination of the blood sample with Wharton jelly
D. Mother having a positive direct antiglobulin test