Which of the following salt solution gives white precipitate turning to black on adding${\mathrm{HgCI}}_2$ solution?

${\mathrm{SnCl}}_2$ salt solution gives white precipitate turning to black on adding${\mathrm{HgCI}}_2$ solution

${\mathrm{SnCl}}_2$ is a powerful reducing agent that decreases

${\mathrm{Hg}}_2{\mathrm{CI}}_2$ to ${\mathrm{HgCI}}_2$

(white), which is then further broken down to Hg (grey).
Following are the responses:

$\begin{array}{l}{\mathrm{SnCl}}_2+{\mathrm{HgCl}}_2\to {\mathrm{SnCl}}_4+{\mathrm{Hg}}_2{\mathrm{Cl}}_2\\ {\mathrm{SnCl}}_2+{\mathrm{Hg}}_2{\mathrm{Cl}}_2\to {\mathrm{SnCl}}_4+2\mathrm{Hg}\end{array}$

Hence option A is correct