Concept:Thermal stability of carbonates and hydrogen carbonates.
Explanation:Group 1 metal carbonates, such as potassium carbonate, are stable to heat.
Potassium trioxocarbonate (IV) is
K2CO3, which does not decompose on heating.
Ammonium chloride sublimes, lead nitrate decomposes, and sodium hydrogen carbonate decomposes to give sodium carbonate, water, and carbon dioxide.
Therefore, only potassium trioxocarbonate (IV) remains undecomposed.
Answer:C. Potassium trioxocarbonate (IV)