Which of the following is the correct chemical formula for slag?

In the extraction of copper,metal is formed in the Bessemer converter due to the reaction:

Which of the following has the lowest percentage of carbon?

Write the chemical reactions involved in the extraction of gold by the cyanide process. Also,explain the role of zinc in this extraction.

In the commercial electrochemical process for aluminium extraction,the electrolyte used is:

The compound$(s)$ that is(are) removed as slag during the extraction of copper is:
$1. CaO$
$2. FeO$
$3. Al_{2}O_{3}$
$4. ZnO$
$5. NiO$
Choose the correct answer from the options given below.