What is Thomas slag?

Match List-$I$ and List-$II$ and select the correct answer using the codes given below the lists :

List-$I$	List-$II$
$I.$ Cyanide process	$(1)$ Ultrapure $Ge$
$II.$ Floatation process	$(2)$ Dressing of $HgS$
$III.$ Electrolytic reduction	$(3)$ Extraction of $Al$
$IV.$ Zone refining	$(4)$ Extraction of $Au$

Which one of the following statements is incorrect?

Which among the following statement$(s)$ is(are) true for the extraction of aluminium from bauxite?
$A$. Hydrated $Al_2O_3$ precipitates,when $CO_2$ is bubbled through a solution of sodium aluminate.
$B$. Addition of $Na_3AlF_6$ lowers the melting point of alumina.
$C$. $CO_2$ is evolved at the anode during electrolysis.
$D$. The cathode is a steel vessel with a lining of carbon.

Identify the reaction,which is not related to the extraction of copper.

Identify the metal which is not common to German silver and brass.