4. A pendulum is formed by pivoting a long thin rod of length L and mass M about a point on the rod. Apparently, the period (T) of this pendulum (for small oscillations) depends on the position of the pivot. Suppose the pivot is at a distance d from the center of the rod. What d would give a minimum T? (The moment of inertia of a thin rod about its center is ML²/12)
(A) L/√6
(B) L/6
(C) L/√12
(D) L/12
(E) None of the above.