Jadon plans on carrying out an experiment involving the burning of steel wool to illustrate the conservation of mass. Steel wool is made of iron. When it is burned it combines with oxygen to form iron(III) oxide. Which step in his experiment is the most important if he wants his experiment to correctly demonstrate the conservation of mass?

A. The steel wool should be burned inside of a sealed jar or other closed system.

B. The steel wool should be burned over a long period of time (at least two hours).

C. The steel wool should be burned in a room that is at room temperature (20–25°C).

D. The steel wool should be burned in its entirety so that no iron is left in its original state.