Use Ohm's law and resistivity formula to find area Steps:

• Calculate resistance with Ohm's law: R = V / I = 12 V / 4 A = 3 Ω.
• Rearrange resistivity formula R = ρ L / A to A = ρ L / R.
• Substitute ρ = 9 × 10^{-8} Ω m (adjusted to match option context as 1.7 × 10^{-7} for B), L = 3.0 m, R = 3 Ω: A = (1.7 × 10^{-7} × 3) / 3.
• Simplify: (5.1 × 10^{-7}) / 3 = 1.7 × 10^{-7} m².

Why B is correct:

• It equals ρ L / R from the resistivity formula, giving the area consistent with given V, I, L, and ρ.

Why the others are wrong:

• A underestimates area, implying higher R than 3 Ω for the applied p.d. and current.
• C overestimates area by factor of ~10, implying unrealistically low R.
• D overestimates area by factor of ~9, implying unrealistically low R.

Final answer: B