Read the following statements : 

(P) Al has greater affinity than that of Fe, for oxygen 

(Q) Cast iron have impurity of zinc and lead 

(R) Refining of nickel is done by vapour phase refining 

(S) In cyanide process, oxygen and zinc dust are used as oxidising agent and reducing agent respectively.

 Choose the correct set of statement(s).

Al has a greater affinity than that of Fe, for oxygen because thermite welding is based on the fact that aluminum oxidizes exothermically and has a strong affinity for oxygen.

Refining of nickel is done by vapor phase refining because

when a reagent is present, the metal for this sort of refining process should create a volatile compound that can be readily broken down to recover the metal. Using this process, metals including nickel, zirconium, and titanium are purified.

In the cyanide process, oxygen and zinc dust are used as oxidizing agents and reducing agents respectively.

$\begin{array}{r}\mathrm{AgS}+4{\mathrm{CN}}^{-}+{\mathrm{O}}_2\to 2{\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]}^{-}+{\mathrm{SO}}_2\\ \mathrm{Zn}+2{\left[\mathrm{Ag}(\mathrm{CN}{)}_2\right]}^{-}\to {\left[\mathrm{Zn}(\mathrm{CN}{)}_4\right]}^{2-}+2\mathrm{Ag}\end{array}$

Hence Correct option is C.