Which of the following statements is not correct ?

Question

$\begin {array} {1 1} (A)\;\text{Mercury (II) chloride is sparingly soluble in cold water but dissolves readily in hot water} \\ (B)\;\text{Mercury (II) chloride is first reduced to white mercury (I) chloride and then to grey metallic mercury when treated with tin (II) chloride} \\ (C)\;\text{Nessler's reagent which is an aqueous solution of $K_2[Hgl_4]$ is used to test ammonium salts } \\ (D)\;\text{$HgCl_2$ sublimes on heating} \end {array}$