Which of the following molecules exists as a cyclic trimer in the solid state?

The highest catenation ability is shown by

Match List-$I$ with List-$II$ :

List-$I$ (Oxoacids of Sulphur)	List-$II$ (Bonds)
$A$. Peroxodisulphuric acid	$I$. Two $S-OH$,Four $S=O$,One $S-O-S$
$B$. Sulphuric acid	$II$. Two $S-OH$,One $S=O$
$C$. Pyrosulphuric acid	$III$. Two $S-OH$,Four $S=O$,One $S-O-O-S$
$D$. Sulphurous acid	$IV$. Two $S-OH$,Two $S=O$

Choose the correct answer from the options given below.

The key step in the manufacturing of $H_2SO_4$ by contact process is

Explain the industrial manufacturing of sulphuric acid by the contact process.

Observe the following statements :
$a$. The thermal stability of hydrides of group $16$ elements follows the order :
$H_2O > H_2S > H_2Se > H_2Te$
$b$. Acidic nature of hydrides of group $16$ elements follows the order :
$H_2O < H_2S < H_2Se < H_2Te$
$c$. The reducing nature of $H_2S$,$H_2Se$ and $H_2Te$ follows the order :
$H_2S < H_2Se < H_2Te$
The correct statements are: