Aluminium Meets Both Aircraft Metal Requirements

Steps:

• Identify requirement 1: low density reduces aircraft weight for better fuel efficiency.
• Check aluminium's density: 2.7 g/cm³, lower than iron (7.9 g/cm³) or steel.
• Identify requirement 2: corrosion resistance prevents structural weakening in harsh environments.
• Verify aluminium's corrosion resistance: forms a natural oxide layer that protects against oxidation.

Why A is correct:

• Aluminium's density (2.7 g/cm³) is relatively low per material science standards, and its passive Al₂O₃ oxide layer provides inherent corrosion resistance, satisfying both conditions.

Why the others are wrong:

• B: Aluminium also resists corrosion via oxide formation, not just low density.
• C: Aluminium has low density (2.7 g/cm³), not solely corrosion resistance.
• D: Aluminium satisfies both properties essential for aircraft.

Final answer: A