The correct option is C Na > Mg > Fe > Au
Sodium (Na) is the most reactive element amongst the other three because sodium reacts violently even with the cold water.
Magnesium (Mg) on the otherhand reacts to a very little extent to the warm water.
Red hot iron (Fe) reacts with steam at high temperature.
And lastly, gold (Au) is a noble metal, it barely reacts with the steam also.