Which of the following statements is correct?
- ANoble gases are unreactive because they all have eight electrons in their outer shells.
- BThe Group VII element astatine, $\text{At}_2$, is expected to be a black solid at room temperature.
- CThe reactivity of the elements in both Group I and Group VII increases down the group.
- DWhen aqueous chlorine is added to aqueous potassium bromide, there is no change in colour.