What is the percentage of carbon in mild steel?

Given below are two statements:
Statement $I$: During electrolytic refining,the pure metal is made to act as anode and its impure metallic form is used as cathode.
Statement $II$: During the Hall-Heroult electrolysis process,purified $Al_2O_3$ is mixed with $Na_3AlF_6$ to lower the melting point of the mixture.
In the light of the above statements,choose the most appropriate answer from the options given below:

Ellingham diagrams can be drawn for which of the following?

Which of the following statement$(s)$ is/are incorrect?

What is Thomas slag?

Spiegeleisen is an alloy of