Which of the following substances conducts electricity the most?

Correct answer: c Silver

Silver has the least specific resistance (1.59×10⁻⁸ Ω m), so it is the best conductor.

Why the other options are wrong

• a Gold: Gold has ρ = 2.44×10⁻⁸ Ω m, more than silver and copper, so it conducts less.
• b Copper: Copper has ρ = 1.68×10⁻⁸ Ω m, a little more than silver (1.59×10⁻⁸), so silver conducts better.
• d Graphite: Graphite has ρ = 2.50×10⁻⁶ Ω m, far more than the metals, so it conducts less.