Explain why removing either air or water can prevent the rusting of iron.

Removing air prevents rusting because oxygen is essential for the chemical reaction that leads to rust formation. Similarly, if water is removed, the necessary moisture for the reaction is absent, stopping rusting. Therefore, both air and water must be present for rusting to occur.

This question assesses the student's ability to explain the chemical processes involved in rusting. The answer effectively connects the absence of air or water to the prevention of rusting, reinforcing the understanding of corrosion mechanisms.