Resistance inversely proportional to area, with constant volume

Steps:

• Resistance of cylinder: R = ρ L / A, where ρ is constant resistivity.
• Volume V = A L is constant, so A = V / L.
• Substitute A into R: R = ρ L / (V / L) = (ρ / V) L².
• R ∝ L², so graph is upward parabola.

Why D is correct:

• D shows quadratic increase, matching R = (ρ / V) L² from Ohm's law and constant volume.

Why the others are wrong:

• A: Linear increase assumes constant A, but A decreases as L increases.
• B: Linear decrease contradicts R increasing with L.
• C: Constant R implies no length dependence, ignoring formula.

Final answer: D