Which is the most stable crystalline form of sulfur at room temperature?

In the preparation of $H_2SO_4$ by the Contact Process,why is $SO_3$ not absorbed directly in water to form $H_2SO_4$?

Which element from the following does $NOT$ belong to the chalcogen family?

Assertion: The reaction between $SO_2$ and $H_2S$ in the presence of $Fe_2O_3$ catalyst gives elemental sulfur.
Reason: $SO_2$ is a reducing agent.

Explain variations in atomic radii and ionisation enthalpies in group-$16$.

The compound$(s)$ having peroxide linkage is(are):
$(A)$ $H_2S_2O_7$
$(B)$ $H_2S_2O_8$
$(C)$ $H_2S_2O_5$
$(D)$ $H_2SO_5$