Photochromic glass, which is used for sunglasses, becomes darker when it is exposed to bright light and then returns to being more transparent when the light is weaker. The darkening of the glass is caused by the presence of silver atoms. The reactions below are involved. Reaction 1: $\text{Ag}^+ + \text{Cl}^- \rightleftharpoons \text{Ag} + \text{Cl}$. Reaction 2: $\text{Cu}^+ + \text{Cl} \rightarrow \text{Cu}^{2+} + \text{Cl}^-$. Reaction 3: $\text{Cu}^{2+} + \text{Ag} \rightarrow \text{Cu}^+ + \text{Ag}^+$. Which statement about these reactions is correct?
- A$\text{Cu}^+$ and $\text{Cu}^{2+}$ ions act as catalysts.
- B$\text{Cu}^+$ ions act as an oxidising agent in reaction 2.
- CReaction 3 increases the darkness of the glass.
- DSilver atoms are reduced in reaction 3.