What Is the Schilling Test

What is the Schilling test?

A) The administration of radioactive cobalamin and the measurement of its excretion in the urine to test for vitamin B₁₂ deficiency
B) The measurement of antigen-antibody immune complexes in the blood to test for hemolytic anemia
C) The measurement of serum ferritin and total iron-binding capacity in the blood to test for iron deficiency anemia
D) The administration of folate and measurement in 2 hours of its level in a blood sample to test for folic acid deficiency anemia