What is known as Thomas slag?

The advantage$(s)$ of using $O_2$ rather than air in the steel industry is(are):
$(I)$ There is a faster conversion,so a given plant can produce more steel in a day.
$(II)$ Larger quantities can be handled.
$(III)$ It gives a purer product,and the surface is free from nitrides.

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.

Which alloy contains a non-metal?

By annealing,steel

Select the correct statement.