Nitu mixed some iron filings with sulphur powder in a China dish. She heated the contents of China dish. What did she observe during the experiment?

• A.  There was no difference in the contents of China dish before and after heating.
• B.  Before heating, iron filings and sulphur powder could be seen separately but after heating the content became black.
• C.  Because Q is an electrolyte that conducts electricity when it is in the molten state.
• D.  Before heating, the contents were black and after heating, iron filings and sulphur could be seen separately.