C-07-Q102mediumsingle_mcqThe chemical formula of rust is—aFe2O3⋅nH2O\mathrm{Fe_2O_3 \cdot nH_2O}Fe2O3⋅nH2ObFeO⋅H2O\mathrm{FeO \cdot H_2O}FeO⋅H2OcFe(OH)3\mathrm{Fe(OH)_3}Fe(OH)3dFe3O4\mathrm{Fe_3O_4}Fe3O4