The action of concentrated nitric acid $(HNO_3)$ on metallic tin $(Sn)$ produces:

When concentrated $H_2SO_4$ is added to dry $KNO_3$,brown fumes evolve. These fumes are

What happens when excess water is added to a solution of $BiCl_3$?

The element which is essential in nitrogen fixation is

Which of the following is metaphosphoric acid?

Given below are two statements:
Statement $I$: The $N-N$ single bond is weaker and longer than the $P-P$ single bond.
Statement $II$: Compounds of group $15$ elements in $+3$ oxidation state readily undergo disproportionation reactions.
In the light of the above statements,choose the correct answer from the options given below: