Which expression gives the polar moment of inertia J for a hollow circular shaft with outer diameter D and inner diameter d?

• A. J = π/32 * D^4
• B. J = π/32 * (D^4 - d^4)
• C. J = π/16 * (D^4 - d^4)
• D. J = π/64 * (D^4 - d^4)

Answer: (B)