Which of the following elements shows polymorphism?

Which of the following elements exhibits the highest property of catenation?

Which of the following oxoacids of sulfur contains a sulfur-sulfur $(S-S)$ double bond?

Justify the placement of $O$,$S$,$Se$,$Te$,and $Po$ in the same group of the periodic table in terms of electronic configuration,oxidation state,and hydride formation.

What is produced by the dehydration of concentrated $H_2SO_4$ in the presence of $P_4O_{10}$?

Acidity of diprotic acids in aqueous solutions increases in the order: