Among the following the elements which exhibit variable valences 1 & 2 are

There are some elements which show different valences in different compounds. Ex: Cu, Fe, Hg, Ag

$\mathrm{Cu}\left(\mathrm{I}\right) \mathrm{in} {\mathrm{Cu}}_2{\mathrm{Cl}}_2,\mathrm{Cu}\left(\mathrm{II}\right) \mathrm{in} {\mathrm{CuCl}}_2$

$\mathrm{Ag}\left(\mathrm{I}\right) \mathrm{in} \mathrm{AgCl},\mathrm{Ag}\left(\mathrm{II}\right)\mathrm{in} {\mathrm{AgCl}}_2;\mathrm{Hg}\left(\mathrm{I}\right) \mathrm{in} {\mathrm{Hg}}_2{\mathrm{Cl}}_2,\mathrm{Hg}\left(\mathrm{II}\right) \mathrm{in} {\mathrm{HgCl}}_2$