Answer:The correct answer is option(C).
Step-by-step explanation:
Compound is a substance made up of two or more elements which are chemically joined together.
When the iron and sulfur heated together in the test tube a chemical reaction reaction took place between the iron and sulfur which lead to the formation of iron sulfur compound (here black mass).And this compound will differ in chemical proprieties with respect to its constituting pure element.
When the magnet was brought near to it , it doesn't attracted the black mass towards itself.This is because the 'The black mass is a compound and no longer retains the properties of iron'.