The correct option is A Laminating core
Eddy currents need a surface area to flow. By laminating, we reduce the material and provide space for winding the wires around it to make coils. The cuts made, reduce the surface area in which eddy currents can flow. This not only decreases the eddy currents but also decreases the power dissipated by them. So, laminating core is the best method to decrease eddy currents.