The correct answer is B) Low reactivity.
Nitrogen is used to protect steel from water because nitrogen has low reactivity.
Nitrogen molecules are resistant form water. It is a colorless, odorless and tasteless element. The Earth has almost 80% of the nitrogen in the atmosphere. This nitrogen was is used as an inert replacement for air when there is no need for oxidation or preparing samples of chemical analysis to reduce the volume of liquid. Nitrogen is also used to protect steel from water because nitrogen has low reactivity.