18. A slender metal rod of length L rotates with an angular speed of ω about an axis through one end and perpendicular to the rod. The plane of rotation of the rod is perpendicular to a uniform magnetic field with a magnitude of B. Which statement is not correct for this system? (A) The induced emf in the rod is ωBL2 ； (B) The potential difference between its ends is ωBL2/2 ； (C) The induced emf in the rod is equal to the potential difference between its ends； (D) All； (E) None.