Which reaction is described as endothermic?
- A$\text{Ca(OH)}_2(aq) + 2\text{HCl}(aq) \rightarrow \text{CaCl}_2(aq) + 2\text{H}_2\text{O}(l)$
- B$2\text{Cl}(g) \rightarrow \text{Cl}_2(g)$
- C$2\text{Ca}(s) + \text{O}_2(g) \rightarrow 2\text{CaO}(s)$
- D$\text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g)$