An element $\mathrm{X}$ forms two oxides $\mathrm{X}\mathrm{O}$ and ${\mathrm{X}\mathrm{O}}_2$. The oxide $\mathrm{X}\mathrm{O}$ is neutral but ${\mathrm{X}\mathrm{O}}_2$ is acidic in nature. The element $\mathrm{X}$ is most likely to be:

A metal less reactive and another metal more reactive than hydrogen are:

An element $\mathrm{E}$ reacts with water to form a solution which turns phenolphthalein solution pink. The element $\mathrm{E}$ is most likely to be: