Which of the following is a good reducing agent?

Sulphur dioxide on reaction with chlorine in the presence of charcoal gives compound $(A)$. This on reaction with white phosphorus gives $SO_2$ and compound $(B)$. The correct statement about '$B$' is

Which halogen can be oxidised by concentrated nitric acid?

Which of the following species represent a mixed anhydride?

The correct decreasing order of boiling point of hydrogen halides is

Given below are two statements: Statement $(I)$: Oxidising power of halogens decreases in the order $F_2 > Cl_2 > Br_2 > I_2$, which is the basis of "Layer test". Statement $(II)$: "Layer test" to identify $Br_2$ and $I_2$ in aqueous solution involves the oxidation of bromide or iodide into $Br_2$ or $I_2$ respectively with $Cl_2$, which is a type of displacement redox reaction. In the light of the above statements, choose the correct answer from the options given below: