Brass is an alloy of copper and ......... .

Stainless steel is an alloy of iron with:

Given below are two statements:
Statement $I$: During electrolytic refining,the pure metal is made to act as anode and its impure metallic form is used as cathode.
Statement $II$: During the Hall-Heroult electrolysis process,purified $Al_2O_3$ is mixed with $Na_3AlF_6$ to lower the melting point of the mixture.
In the light of the above statements,choose the most appropriate answer from the options given below:

$A$ piece of steel is heated until redness and then plunged into cold water or oil. This treatment of iron makes it:

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. Concentration of gold ore	$I$. Aniline
$B$. Leaching of alumina	$II$. $NaOH$
$C$. Froth stabiliser	$III$. $SO_2$
$D$. Blister copper	$IV$. $NaCN$

Choose the correct answer from the options given below.

What are the metals and their approximate percentages in German silver?