C-10-Q156mediumsingle_mcqH2S2O7+H2O→?\mathrm{H_2S_2O_7 + H_2O \to ?}H2S2O7+H2O→?a2H2SO4\mathrm{2H_2SO_4}2H2SO4bH2SO3\mathrm{H_2SO_3}H2SO3c2SO3\mathrm{2SO_3}2SO3dH2S\mathrm{H_2S}H2S