Which of the following is not a basic flux?

Refractory materials are generally used in furnaces because

What is the percentage $(\%)$ of silver in German silver?

The correct option$(s)$ related to the extraction of iron from its ore in the blast furnace operating in the temperature range $900-1500 \ K$ is(are):
$(A)$ Limestone is used to remove silicate impurity.
$(B)$ Pig iron obtained from blast furnace contains about $4 \%$ carbon.
$(C)$ Coke $(C)$ converts $CO_2$ to $CO$.
$(D)$ Exhaust gases consist of $NO_2$ and $CO$.

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

Metals are extracted by other methods through the formation of complexes. The complexes formed in these methods are: $I$: Cyanide process,$II$: Mond process,$III$: Photographic fixing process.