$\begin {array} {1 1} (A)\;\text{Mercury (II) oxide exists in two forms - a red variety and a yellow variety} \\ (B)\;\text{The difference in colour of the two varieties of HgO is due to the particle size - the particles of red variety are smaller} \\ (C)\;\text{The varieties of HgO have the same crystalline structure} \\ (D)\;\text{Red HgO is used as pigment} \end {array}$
