Nitric oxide $(NO)$ is prepared by the action of dilute $HNO_3$ on which of the following metals?

The maximum covalency of a non-metallic group $15$ element '$E$' with the weakest $E-E$ bond is:

When calomel reacts with $NH_4OH$ solution,the compound formed is

Which of the following compounds is the most explosive?

Which of the following is a tetrabasic acid?

When a brown compound of manganese $(A)$ is treated with $HCl$,it gives a gas $(B)$. The gas taken in excess,reacts with $NH_3$ to give an explosive compound $(C)$. Identify compounds $A$,$B$,and $C$.