Which alloy contains $Cu$,$Sn$,and $Zn$?

Metallurgy is the process of

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

Consider the following statements:
$(i)$ Froth flotation technique is used to concentrate sulphide ore.
$(ii)$ Froth flotation technique is based upon differential wettability of ore and impurity in water.
$(iii)$ Red Bauxite is concentrated by Bayer's process.
$(iv)$ Carbon is used as a reducing agent during the extraction of zinc from zinc blende.
Which of the following statements are correct?

In the metallurgy of iron,when limestone is added to the blast furnace,the calcium ions end up in:

Which one of the following reactions does not occur during the extraction of copper?