When ${\text{NaHCO}}_3$ is heated , + ${\text{CO}}_2+{\text{H}}_2\text{O}$ is obtained.

The correct option is A ${\text{Na}}_2{\text{CO}}_3$
Sodium bicarbonate on heating gives out sodium carbonate, carbon dioxide and water. The reaction takes place as follows:

${\text{2NaHCO}}_3\text{(s)}\stackrel{\text{Heat}}{\to }{\text{Na}}_2{\text{CO}}_3\text{(s)}+{\text{CO}}_2\text{(g)}+{\text{H}}_2\text{O}\text{(l)}$