Aluminium's oxide layer enables safe use in cookware

Steps:

• Identify the key issue: aluminium's apparent non-reactivity despite being reactive, suitable for saucepans.
• Recall that aluminium reacts with oxygen to form a thin, impermeable oxide layer.
• Recognize this layer acts as a barrier, preventing further reaction with air or food.
• Match to option A, as it directly explains the lack of reactivity.

Why A is correct:

• The oxide layer passivates the metal surface, blocking corrosion per the definition of passivation in electrochemistry.

Why the others are wrong:

• B: Low density explains lightness but not reactivity.
• C: Density and conductivity relate to weight and wiring, not corrosion resistance.
• D: Group III position indicates reactivity potential but not the protective mechanism.

Final answer: A