The correct option is Carbon dioxide.
Explanation
The question pertains to the chemical properties and applications of Sodium Hydrogencarbonate ($NaHCO_3$), commonly known as baking soda, specifically its behavior under thermal decomposition.
Detailed Analysis:
- Sodium hydrogencarbonate is widely used in cooking as a leavening agent.
- When heated during the cooking process, it undergoes a thermal decomposition reaction.
- The reaction produces sodium carbonate ($Na_2CO_3$), water ($H_2O$), and carbon dioxide ($CO_2$) gas.
- The chemical equation for this reaction is:
$2NaHCO_3 \xrightarrow{\text{Heat}} Na_2CO_3 + H_2O + CO_2 \uparrow$ - The carbon dioxide gas produced gets trapped inside the dough or batter, creating bubbles. This process causes the mixture to rise and results in a soft and spongy texture in cakes and breads.
Key Takeaway: Sodium hydrogencarbonate (baking soda) releases carbon dioxide upon heating, which is the primary agent responsible for the rising of dough in baking.