Which of the following does not give metal oxide on heating?

${\mathrm{K}}_2{\mathrm{CO}}_3$ does not give metal oxide on heating.

The reaction of thermal decomposition of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ is ${\mathrm{Na}}_2{\mathrm{CO}}_3\left(s\right)\to {\mathrm{Na}}_2\mathrm{O}\left(s\right)+{\mathrm{CO}}_2\left(g\right)$ The reaction of thermal decomposition of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ is

${\mathrm{K}}_2{\mathrm{CO}}_3\left(s\right)\to \mathrm{K}+\mathrm{O}+\mathrm{CO}$

The reaction of thermal decomposition of  ${\mathrm{Rb}}_2{\mathrm{CO}}_3$ is

${\mathrm{Rb}}_2{\mathrm{CO}}_3\left(s\right)\to {\mathrm{Rb}}_2\mathrm{O}\left(s\right)+{\mathrm{CO}}_2\left(g\right)$

Hence, ${\mathrm{K}}_2{\mathrm{CO}}_3$ does not give metal oxide on heating.