Which of the following statements is/are incorrect ?
A. A filter paper moistened with cadmium acetate solution turns yellow, when brought in contact with `H_(2)S` gas.
B. Both carbonate ions as well as bicarbonate ions in the solutions, give reddish-brown precipitate with mercury (II) chloride.
C. Sulphites in presence of zinc, reacts with dilute `H_(2)SO_(4)` to liberate `SO_(3)` gas.
D. A filter paper moistened with `KIO_(3)` and starch turns blue in contact with `SO_(2)` vapours.