A single displacement reaction is represented by ${\mathrm{X}}_{\left(\mathrm{s}\right)}+2{\mathrm{HCl}}_{\left(\mathrm{aq}\right)}\to {\mathrm{XCl}}_{2\left(\mathrm{aq}\right)}+{\mathrm{H}}_{2\left(\mathrm{g}\right)}$. Which of the following(s) could be $\mathrm{X}$? Choose the best pair.

i) $\mathrm{Zn}$

ii) $\mathrm{Ag}$

iii) $\mathrm{Cu}$

iv) $\mathrm{Mg}$