The correct answer is B) to reduce eddy currents. Transformer cores are laminated to reduce eddy currents that would otherwise be induced in a solid core. Eddy currents are circular electric currents that are generated within the core material due to the changing magnetic field. These eddy currents can cause energy losses and heating within the core, reducing the efficiency of the transformer. By laminating the core, the eddy current paths are broken up, significantly reducing the eddy current losses. The other options are incorrect because: A) reducing secondary flux is not the primary reason for lamination, C) reducing leakage flux is not the main purpose, and D) reducing hysteresis losses, while also important, is not the main reason for lamination.