Chromyl chloride dissolves in NaOH solution to give a yellow solution. The chromate solution changes to blue colour chromium peroxide with hydrogen peroxide.
The reaction will be as follows,
CrO2Cl2+4NaOH→Na2CrO4+2NaCl+2H2OCrO42−+2H++2H2O2→CrO5+3H2O
Hence, option A is the answer.