In some high-grade snacks in the box has a small paper bag, the small paper bag to open, you can see the gray-black powder, some of which has become brown. Will gray and black

A, based on the question of the phenomenon analysis, the gray-black powder for ferrous compounds have reductive, can play a role in antioxidant, so A is correct;

B, iron powder is a black powder, can be slowly oxidized with the oxygen in the air, water to generate red rust, is the deoxidation of freshness, it is B correct;

C, Fe2O3 is a red solid, it is C wrong;

D, iron oxides are antioxidants, will react with stomach acid, affecting health, can not be consumed, so D is correct;

Therefore, the choice: C.