Answer : Option A) Separated using a magnet; magnetism
Explanation :
In the given observations in the virtual lab, the part of the mixture contains iron fillings which can be easily separated by using magnet. The physical property that was used to separate the iron fillings from the mixture is magnetism. Magnetism is the property possessed by magnets to attract the metal(magnetic object) towards itself or repel the magnetic objects.
In this case, the magnetic object was iron fillings and when magnet was moved over the mixture. The iron fillings got stuck to the magnet and it was easy to separate the iron fillings from the mixture. Then only mixture was left without iron fillings.