The carbonates of alkaline earth metals decompose on heating to give

I. $\mathrm{CO}_2$

II. Metal oxide

III. $\mathrm{H}_2 \mathrm{O}$

IV. CO

Borax is converted into crystalline boron by the following steps :

$$ \text { Borax } \xrightarrow[\mathrm{H}_2 \mathrm{O}]{X} \mathrm{H}_3 \mathrm{BO}_3 \xrightarrow{\Delta} \mathrm{~B}_2 \mathrm{O}_3 \xrightarrow[\Delta]{Y} B $$

Identify $X$ and $Y$ respectively.

Buckminister fullerene contains the following $X$ number of six and $Y$ number of five member rings. What is the value of $X$ and $Y$ ?

The average atmospheric residence time is lowest for which of the given the greenhouse gas?