Which non-metal element possesses luster?

During the extraction of iron from hematite in a blast furnace,which substance is obtained as slag?

Which gas is useful for inhibiting bacterial growth?

How can metals be differentiated from non-metals on the basis of any three chemical properties?

$A$ non-metal $A$ is an important constituent of our food and forms two oxides $B$ and $C$. Oxide $B$ is toxic,whereas $C$ causes global warming.
$(a)$ Identify $A$,$B$,and $C$.
$(b)$ To which Group of the Periodic Table does $A$ belong?

Which alloy is used to prepare scientific balance?