shelbiec5205 shelbiec5205 27-02-2024 Biology contestada At birth, an infant has 200 units of IgG antibody against rubella per ml in his blood. He is not exposed to rubella. At 9 weeks of age, what should the concentration be? a. 200 units/ml b. 100 units/ml c. 50 units/ml d. 25 units/ml