The correct option is A Electro-magnetic induction
The phenomenon of producing an emf in a circuit whenever the magnetic flux linked with a coil changes is electromagnetic induction. Electromagnetic induction is the production of an electromotive force (i.e., voltage) across an electrical conductor due to its dynamic interaction with a magnetic field. It has found many applications in technology, including electrical components such as inductors and transformers, and devices such as electric motors and generators.