Point out in which of the following properties oxygen differs from the rest of the members of its family (Group-$16$)

In the preparation of sulphuric acid from sulphur dioxide in the lead chamber process,what substance is used as a catalyst?

Explain the contact process for the manufacture of sulphuric acid.

Concentrated $H_2SO_4$ reacts with $PCl_5$ to produce

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:

Which of the elements listed below occurs in allotropic forms?