Task: Question Answering
Input (English): Question: A mixture of iron (III) chloride and potassium hexacyanoferrate (III) (potassium ferricyanide) is used to detect extremely small amounts of hydrogen peroxide in the water. The presence of H2O2 causes, after a short time, an intense dark blue color. This is because hydrogen peroxide: 
 Options:  <1> It reduces hexacyanoferrate (III) to hexacyanoferrate (II). <2> Oxide to hexacyanoferrate (III). <3> Oxide to iron (III) chloride. <4> Peroxo-cyano form complexes of Fe (III). <5> Oxidize cyanocomplexes to complex cyanate.
Output (English): 1