What is the number of allotropes of selenium?

Given below are two statements: Statement $I$: The covalency of oxygen is generally two but it can exceed up to four. The oxidation state of oxygen in $SO_2$ is $-2$ and in $OF_2$ it is $+2$. Statement $II$: The anomalous behaviour of oxygen when compared to the other elements of group $16$ is due to its small size and high electronegativity. In the light of the above statements, choose the correct answer from the options given below.

List the important sources of sulphur.

There is no $S-S$ bond in

Which of the following statements is incorrect for $H_2SO_4$?

Which of the following reactions is $NOT$ given by $SO_2$?