Which of the following has the greater conductivity?

Correct answer: d Gold

Gold has ρ = 2.44×10⁻⁸ Ω m, the least of these, so the highest conductivity.

Why the other options are wrong

• a Air: Air has ρ = 1.30×10¹⁶ Ω m, the largest, so its conductivity is the least.
• b Diamond: Diamond has ρ = 1.00×10¹² Ω m, many times more than gold, so its conductivity is lower.
• c Graphite: Graphite has ρ = 2.50×10⁻⁶ Ω m, more than gold (2.44×10⁻⁸), so its conductivity is lower.