Which element from the following exhibits the highest number of allotropes?

Which among the following $P$-block elements forms a colourless and odourless hydride?

Which of the following reactions exhibits the reducing property of ozone?

Which oxide is used as a catalyst in the contact process?

$A$ pale yellow solid molecule $(A)$ having crown shape is heated with conc. $H_2SO_4$. It gives a suffocating smell of gas $(B)$,which when passed through starch iodate paper,turns it blue. The gas $(B)$ is:

Write the order of thermal stability of the hydrides of Group $16$ elements.