B

In iron-deficiency anemia, body iron stores are depleted, so serum iron and ferritin fall and the fraction of transferrin that is iron-bound (transferrin saturation) drops. The liver compensatorily makes more transferrin, raising total iron-binding capacity (TIBC) rather than lowering it, so TIBC is the one parameter that does NOT decrease [Zorgati 2009, PMID 20209848].