Which of the Following Is Found in the First Stage

Which of the following is found in the first stage of iron deficiency?

A) Iron stores decline, as assessed by serum ferritin.
B) Hemoglobin levels fall, as assessed by complete blood count.
C) Red blood cell count falls, as assessed by hematocrit count.
D) Hemoglobin synthesis declines, as assessed by erythrocyte protoporphyrin.
E) Erythrocyte protoporphyrin, begins to accumulate.