What is the use of the slot in the rotor? a) for inserting the field windings b) for inserting the armature windings c) for securing the field windings d) for inserting and securing the field windings

What is the use of the slot in the rotor? a) for inserting the field windings b) for inserting the armature windings c) for securing the field windings d) for inserting and securing the field windings