Calcium hydroxide reacts with carbon dioxide to form.

The correct option is A

Calcium carbonate and water.

The explanation for the correct option.

1. Calcium hydroxide Ca(OH)₂ is a base and CO₂ is acidic in nature
2. As we know from the neutralization reaction that when acid and base react with each other, they form salt and water.
3. Similarly, Calcium hydroxide Ca(OH)₂ reacts with CO₂ to form salt calcium carbonate CaCO₃ and water H₂O.

$$\begin{gathered} \mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right) \\ \mathrm{Calcium}\mathrm{hydroxide}\mathrm{carbon}\mathrm{dioxide}\mathrm{calcium}\mathrm{water} \\ \mathrm{carbonate} \end{gathered}$$

The explanation for the incorrect option.

1. The reaction between calcium hydroxide and carbon dioxide leads to the formation of Calcium Carbonate and water, no evolution of hydrogen gas (H₂) and neither formation of calcium bicarbonate takes place. Therefore, other options are wrong.

Since the reaction between calcium hydroxide $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$and carbon dioxide ${\mathrm{CO}}_2$ leads to the formation of Calcium Carbonate ${\mathrm{CaCO}}_3$ and water ${\mathrm{H}}_2\mathrm{O}$, hence option (a) is correct.